Attacker Value

Unknown

CVE-2021-39338

CVE ID

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Advisory

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Government or Industry Alert

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Miscellaneous

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Attacker Value

Unknown

(0 users assessed)

Exploitability

Unknown

(0 users assessed)

User Interaction

CVE-2021-39338

Disclosure Date: October 14, 2021 •

(Last updated February 23, 2025) ▾

CVE-2021-39338 CVSS v3 Base Score: 4.8

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MITRE ATT&CK

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Collection

Select any Techniques used:

Data from Local System

Data from Removable Media

Data from Network Shared Drive

Input Capture

Input Capture: Keylogging

Input Capture: GUI Input Capture

Input Capture: Web Portal Capture

Input Capture: Credential API Hooking

Data Staged

Data Staged: Local Data Staging

Data Staged: Remote Data Staging

Screen Capture

Email Collection

Email Collection: Local Email Collection

Email Collection: Remote Email Collection

Email Collection: Email Forwarding Rule

Clipboard Data

Automated Collection

Audio Capture

Video Capture

Man in the Browser

Data from Information Repositories

Data from Information Repositories: Confluence

Data from Information Repositories: Sharepoint

Data from Cloud Storage Object

Man-in-the-Middle

Man-in-the-Middle: LLMNR/NBT-NS Poisoning and SMB Relay

Archive Collected Data

Archive Collected Data: Archive via Utility

Archive Collected Data: Archive via Library

Archive Collected Data: Archive via Custom Method

Command and Control

Select any Techniques used:

Data Obfuscation

Data Obfuscation: Junk Data

Data Obfuscation: Steganography

Data Obfuscation: Protocol Impersonation

Fallback Channels

Application Layer Protocol

Application Layer Protocol: Web Protocols

Application Layer Protocol: File Transfer Protocols

Application Layer Protocol: Mail Protocols

Application Layer Protocol: DNS

Proxy

Proxy: Internal Proxy

Proxy: External Proxy

Proxy: Multi-hop Proxy

Proxy: Domain Fronting

Communication Through Removable Media

Non-Application Layer Protocol

Web Service

Web Service: Dead Drop Resolver

Web Service: Bidirectional Communication

Web Service: One-Way Communication

Multi-Stage Channels

Ingress Tool Transfer

Data Encoding

Data Encoding: Standard Encoding

Data Encoding: Non-Standard Encoding

Traffic Signaling

Traffic Signaling: Port Knocking

Remote Access Software

Dynamic Resolution

Dynamic Resolution: Fast Flux DNS

Dynamic Resolution: Domain Generation Algorithms

Dynamic Resolution: DNS Calculation

Non-Standard Port

Protocol Tunneling

Encrypted Channel

Encrypted Channel: Symmetric Cryptography

Encrypted Channel: Asymmetric Cryptography

Credential Access

Select any Techniques used:

OS Credential Dumping

OS Credential Dumping: LSASS Memory

OS Credential Dumping: Security Account Manager

OS Credential Dumping: NTDS

OS Credential Dumping: LSA Secrets

OS Credential Dumping: Cached Domain Credentials

OS Credential Dumping: DCSync

OS Credential Dumping: Proc Filesystem

OS Credential Dumping: /etc/passwd and /etc/shadow

Network Sniffing

Input Capture

Input Capture: Keylogging

Input Capture: GUI Input Capture

Input Capture: Web Portal Capture

Input Capture: Credential API Hooking

Brute Force

Brute Force: Password Guessing

Brute Force: Password Cracking

Brute Force: Password Spraying

Brute Force: Credential Stuffing

Two-Factor Authentication Interception

Forced Authentication

Exploitation for Credential Access

Steal Application Access Token

Steal Web Session Cookie

Unsecured Credentials

Unsecured Credentials: Credentials In Files

Unsecured Credentials: Credentials in Registry

Unsecured Credentials: Bash History

Unsecured Credentials: Private Keys

Unsecured Credentials: Cloud Instance Metadata API

Unsecured Credentials: Group Policy Preferences

Credentials from Password Stores

Credentials from Password Stores: Keychain

Credentials from Password Stores: Securityd Memory

Credentials from Password Stores: Credentials from Web Browsers

Modify Authentication Process

Modify Authentication Process: Domain Controller Authentication

Modify Authentication Process: Password Filter DLL

Modify Authentication Process: Pluggable Authentication Modules

Man-in-the-Middle

Man-in-the-Middle: LLMNR/NBT-NS Poisoning and SMB Relay

Steal or Forge Kerberos Tickets

Steal or Forge Kerberos Tickets: Golden Ticket

Steal or Forge Kerberos Tickets: Silver Ticket

Steal or Forge Kerberos Tickets: Kerberoasting

Defense Evasion

Select any Techniques used:

Direct Volume Access

Rootkit

Obfuscated Files or Information

Obfuscated Files or Information: Binary Padding

Obfuscated Files or Information: Software Packing

Obfuscated Files or Information: Steganography

Obfuscated Files or Information: Compile After Delivery

Obfuscated Files or Information: Indicator Removal from Tools

Masquerading

Masquerading: Invalid Code Signature

Masquerading: Right-to-Left Override

Masquerading: Rename System Utilities

Masquerading: Masquerade Task or Service

Masquerading: Match Legitimate Name or Location

Masquerading: Space after Filename

Process Injection

Process Injection: Dynamic-link Library Injection

Process Injection: Portable Executable Injection

Process Injection: Thread Execution Hijacking

Process Injection: Asynchronous Procedure Call

Process Injection: Thread Local Storage

Process Injection: Ptrace System Calls

Process Injection: Proc Memory

Process Injection: Extra Window Memory Injection

Process Injection: Process Hollowing

Process Injection: Process Doppelgänging

Process Injection: VDSO Hijacking

Indicator Removal on Host

Indicator Removal on Host: Clear Windows Event Logs

Indicator Removal on Host: Clear Linux or Mac System Logs

Indicator Removal on Host: Clear Command History

Indicator Removal on Host: File Deletion

Indicator Removal on Host: Network Share Connection Removal

Indicator Removal on Host: Timestomp

Valid Accounts

Valid Accounts: Default Accounts

Valid Accounts: Domain Accounts

Valid Accounts: Local Accounts

Valid Accounts: Cloud Accounts

Modify Registry

Trusted Developer Utilities Proxy Execution

Trusted Developer Utilities Proxy Execution: MSBuild

Access Token Manipulation

Access Token Manipulation: Token Impersonation/Theft

Access Token Manipulation: Create Process with Token

Access Token Manipulation: Make and Impersonate Token

Access Token Manipulation: Parent PID Spoofing

Access Token Manipulation: SID-History Injection

Deobfuscate/Decode Files or Information

BITS Jobs

Indirect Command Execution

Traffic Signaling

Traffic Signaling: Port Knocking

Rogue Domain Controller

Exploitation for Defense Evasion

Signed Script Proxy Execution

Signed Script Proxy Execution: PubPrn

Signed Binary Proxy Execution

Signed Binary Proxy Execution: Compiled HTML File

Signed Binary Proxy Execution: Control Panel

Signed Binary Proxy Execution: CMSTP

Signed Binary Proxy Execution: InstallUtil

Signed Binary Proxy Execution: Mshta

Signed Binary Proxy Execution: Msiexec

Signed Binary Proxy Execution: Odbcconf

Signed Binary Proxy Execution: Regsvcs/Regasm

Signed Binary Proxy Execution: Regsvr32

Signed Binary Proxy Execution: Rundll32

XSL Script Processing

Template Injection

File and Directory Permissions Modification

File and Directory Permissions Modification: Windows File and Directory Permissions Modification

File and Directory Permissions Modification: Linux and Mac File and Directory Permissions Modification

Execution Guardrails

Execution Guardrails: Environmental Keying

Group Policy Modification

Virtualization/Sandbox Evasion

Virtualization/Sandbox Evasion: System Checks

Virtualization/Sandbox Evasion: User Activity Based Checks

Virtualization/Sandbox Evasion: Time Based Evasion

Unused/Unsupported Cloud Regions

Pre-OS Boot

Pre-OS Boot: System Firmware

Pre-OS Boot: Component Firmware

Pre-OS Boot: Bootkit

Abuse Elevation Control Mechanism

Abuse Elevation Control Mechanism: Setuid and Setgid

Abuse Elevation Control Mechanism: Bypass User Access Control

Abuse Elevation Control Mechanism: Sudo and Sudo Caching

Abuse Elevation Control Mechanism: Elevated Execution with Prompt

Use Alternate Authentication Material

Use Alternate Authentication Material: Application Access Token

Use Alternate Authentication Material: Pass the Hash

Use Alternate Authentication Material: Pass the Ticket

Use Alternate Authentication Material: Web Session Cookie

Subvert Trust Controls

Subvert Trust Controls: Gatekeeper Bypass

Subvert Trust Controls: Code Signing

Subvert Trust Controls: SIP and Trust Provider Hijacking

Subvert Trust Controls: Install Root Certificate

Modify Authentication Process

Modify Authentication Process: Domain Controller Authentication

Modify Authentication Process: Password Filter DLL

Modify Authentication Process: Pluggable Authentication Modules

Impair Defenses

Impair Defenses: Disable or Modify Tools

Impair Defenses: Disable Windows Event Logging

Impair Defenses: HISTCONTROL

Impair Defenses: Disable or Modify System Firewall

Impair Defenses: Indicator Blocking

Impair Defenses: Disable or Modify Cloud Firewall

Hide Artifacts

Hide Artifacts: Hidden Files and Directories

Hide Artifacts: Hidden Users

Hide Artifacts: Hidden Window

Hide Artifacts: NTFS File Attributes

Hide Artifacts: Hidden File System

Hide Artifacts: Run Virtual Instance

Hijack Execution Flow

Hijack Execution Flow: DLL Search Order Hijacking

Hijack Execution Flow: DLL Side-Loading

Hijack Execution Flow: Dylib Hijacking

Hijack Execution Flow: Executable Installer File Permissions Weakness

Hijack Execution Flow: LD_PRELOAD

Hijack Execution Flow: Path Interception by PATH Environment Variable

Hijack Execution Flow: Path Interception by Search Order Hijacking

Hijack Execution Flow: Path Interception by Unquoted Path

Hijack Execution Flow: Services File Permissions Weakness

Hijack Execution Flow: Services Registry Permissions Weakness

Hijack Execution Flow: COR_PROFILER

Modify Cloud Compute Infrastructure

Modify Cloud Compute Infrastructure: Create Snapshot

Modify Cloud Compute Infrastructure: Create Cloud Instance

Modify Cloud Compute Infrastructure: Delete Cloud Instance

Modify Cloud Compute Infrastructure: Revert Cloud Instance

Discovery

Select any Techniques used:

System Service Discovery

Application Window Discovery

Query Registry

System Network Configuration Discovery

Remote System Discovery

System Owner/User Discovery

Network Sniffing

Network Service Scanning

System Network Connections Discovery

Process Discovery

Permission Groups Discovery

Permission Groups Discovery: Local Groups

Permission Groups Discovery: Domain Groups

Permission Groups Discovery: Cloud Groups

System Information Discovery

File and Directory Discovery

Account Discovery

Account Discovery: Local Account

Account Discovery: Domain Account

Account Discovery: Email Account

Account Discovery: Cloud Account

Peripheral Device Discovery

System Time Discovery

Network Share Discovery

Password Policy Discovery

Browser Bookmark Discovery

Domain Trust Discovery

Virtualization/Sandbox Evasion

Virtualization/Sandbox Evasion: System Checks

Virtualization/Sandbox Evasion: User Activity Based Checks

Virtualization/Sandbox Evasion: Time Based Evasion

Software Discovery

Software Discovery: Security Software Discovery

Cloud Service Discovery

Cloud Service Dashboard

Execution

Select any Techniques used:

Windows Management Instrumentation

Scheduled Task/Job

Scheduled Task/Job: At (Linux)

Scheduled Task/Job: At (Windows)

Scheduled Task/Job: Cron

Scheduled Task/Job: Launchd

Scheduled Task/Job: Scheduled Task

Command and Scripting Interpreter

Command and Scripting Interpreter: PowerShell

Command and Scripting Interpreter: AppleScript

Command and Scripting Interpreter: Windows Command Shell

Command and Scripting Interpreter: Unix Shell

Command and Scripting Interpreter: Visual Basic

Command and Scripting Interpreter: Python

Command and Scripting Interpreter: JavaScript/JScript

Software Deployment Tools

Native API

Shared Modules

Exploitation for Client Execution

User Execution

User Execution: Malicious Link

User Execution: Malicious File

Inter-Process Communication

Inter-Process Communication: Component Object Model

Inter-Process Communication: Dynamic Data Exchange

System Services

System Services: Launchctl

System Services: Service Execution

Exfiltration

Select any Techniques used:

Exfiltration Over Other Network Medium

Exfiltration Over Other Network Medium: Exfiltration Over Bluetooth

Automated Exfiltration

Scheduled Transfer

Data Transfer Size Limits

Exfiltration Over C2 Channel

Exfiltration Over Alternative Protocol

Exfiltration Over Alternative Protocol: Exfiltration Over Symmetric Encrypted Non-C2 Protocol

Exfiltration Over Alternative Protocol: Exfiltration Over Asymmetric Encrypted Non-C2 Protocol

Exfiltration Over Alternative Protocol: Exfiltration Over Unencrypted/Obfuscated Non-C2 Protocol

Exfiltration Over Physical Medium

Exfiltration Over Physical Medium: Exfiltration over USB

Transfer Data to Cloud Account

Exfiltration Over Web Service

Exfiltration Over Web Service: Exfiltration to Code Repository

Exfiltration Over Web Service: Exfiltration to Cloud Storage

Impact

Select any Techniques used:

Data Destruction

Data Encrypted for Impact

Service Stop

Inhibit System Recovery

Defacement

Defacement: Internal Defacement

Defacement: External Defacement

Firmware Corruption

Resource Hijacking

Network Denial of Service

Network Denial of Service: Direct Network Flood

Network Denial of Service: Reflection Amplification

Endpoint Denial of Service

Endpoint Denial of Service: OS Exhaustion Flood

Endpoint Denial of Service: Service Exhaustion Flood

Endpoint Denial of Service: Application Exhaustion Flood

Endpoint Denial of Service: Application or System Exploitation

System Shutdown/Reboot

Account Access Removal

Disk Wipe

Disk Wipe: Disk Content Wipe

Disk Wipe: Disk Structure Wipe

Data Manipulation

Data Manipulation: Stored Data Manipulation

Data Manipulation: Transmitted Data Manipulation

Data Manipulation: Runtime Data Manipulation

Initial Access

Select any Techniques used:

Valid Accounts

Valid Accounts: Default Accounts

Valid Accounts: Domain Accounts

Valid Accounts: Local Accounts

Valid Accounts: Cloud Accounts

Replication Through Removable Media

External Remote Services

Drive-by Compromise

Exploit Public-Facing Application

Supply Chain Compromise

Supply Chain Compromise: Compromise Software Dependencies and Development Tools

Supply Chain Compromise: Compromise Software Supply Chain

Supply Chain Compromise: Compromise Hardware Supply Chain

Trusted Relationship

Hardware Additions

Phishing

Phishing: Spearphishing Attachment

Phishing: Spearphishing Link

Phishing: Spearphishing via Service

Lateral Movement

Select any Techniques used:

Remote Services

Remote Services: Remote Desktop Protocol

Remote Services: SMB/Windows Admin Shares

Remote Services: Distributed Component Object Model

Remote Services: SSH

Remote Services: VNC

Remote Services: Windows Remote Management

Software Deployment Tools

Taint Shared Content

Replication Through Removable Media

Exploitation of Remote Services

Internal Spearphishing

Use Alternate Authentication Material

Use Alternate Authentication Material: Application Access Token

Use Alternate Authentication Material: Pass the Hash

Use Alternate Authentication Material: Pass the Ticket

Use Alternate Authentication Material: Web Session Cookie

Remote Service Session Hijacking

Remote Service Session Hijacking: SSH Hijacking

Remote Service Session Hijacking: RDP Hijacking

Lateral Tool Transfer

Persistence

Select any Techniques used:

Boot or Logon Initialization Scripts

Boot or Logon Initialization Scripts: Logon Script (Windows)

Boot or Logon Initialization Scripts: Logon Script (Mac)

Boot or Logon Initialization Scripts: Network Logon Script

Boot or Logon Initialization Scripts: Rc.common

Boot or Logon Initialization Scripts: Startup Items

Scheduled Task/Job

Scheduled Task/Job: At (Linux)

Scheduled Task/Job: At (Windows)

Scheduled Task/Job: Cron

Scheduled Task/Job: Launchd

Scheduled Task/Job: Scheduled Task

Valid Accounts

Valid Accounts: Default Accounts

Valid Accounts: Domain Accounts

Valid Accounts: Local Accounts

Valid Accounts: Cloud Accounts

Account Manipulation

Account Manipulation: Additional Azure Service Principal Credentials

Account Manipulation: Exchange Email Delegate Permissions

Account Manipulation: Add Office 365 Global Administrator Role

Account Manipulation: SSH Authorized Keys

External Remote Services

Create Account

Create Account: Local Account

Create Account: Domain Account

Create Account: Cloud Account

Office Application Startup

Office Application Startup: Office Template Macros

Office Application Startup: Office Test

Office Application Startup: Outlook Forms

Office Application Startup: Outlook Home Page

Office Application Startup: Outlook Rules

Office Application Startup: Add-ins

Browser Extensions

BITS Jobs

Traffic Signaling

Traffic Signaling: Port Knocking

Server Software Component

Server Software Component: SQL Stored Procedures

Server Software Component: Transport Agent

Server Software Component: Web Shell

Implant Container Image

Pre-OS Boot

Pre-OS Boot: System Firmware

Pre-OS Boot: Component Firmware

Pre-OS Boot: Bootkit

Create or Modify System Process

Create or Modify System Process: Launch Agent

Create or Modify System Process: Systemd Service

Create or Modify System Process: Windows Service

Create or Modify System Process: Launch Daemon

Event Triggered Execution

Event Triggered Execution: Change Default File Association

Event Triggered Execution: Screensaver

Event Triggered Execution: Windows Management Instrumentation Event Subscription

Event Triggered Execution: .bash_profile and .bashrc

Event Triggered Execution: Trap

Event Triggered Execution: LC_LOAD_DYLIB Addition

Event Triggered Execution: Netsh Helper DLL

Event Triggered Execution: Accessibility Features

Event Triggered Execution: AppCert DLLs

Event Triggered Execution: AppInit DLLs

Event Triggered Execution: Application Shimming

Event Triggered Execution: Image File Execution Options Injection

Event Triggered Execution: PowerShell Profile

Event Triggered Execution: Emond

Event Triggered Execution: Component Object Model Hijacking

Boot or Logon Autostart Execution

Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder

Boot or Logon Autostart Execution: Authentication Package

Boot or Logon Autostart Execution: Time Providers

Boot or Logon Autostart Execution: Winlogon Helper DLL

Boot or Logon Autostart Execution: Security Support Provider

Boot or Logon Autostart Execution: Kernel Modules and Extensions

Boot or Logon Autostart Execution: Re-opened Applications

Boot or Logon Autostart Execution: LSASS Driver

Boot or Logon Autostart Execution: Shortcut Modification

Boot or Logon Autostart Execution: Port Monitors

Boot or Logon Autostart Execution: Plist Modification

Compromise Client Software Binary

Hijack Execution Flow

Hijack Execution Flow: DLL Search Order Hijacking

Hijack Execution Flow: DLL Side-Loading

Hijack Execution Flow: Dylib Hijacking

Hijack Execution Flow: Executable Installer File Permissions Weakness

Hijack Execution Flow: LD_PRELOAD

Hijack Execution Flow: Path Interception by PATH Environment Variable

Hijack Execution Flow: Path Interception by Search Order Hijacking

Hijack Execution Flow: Path Interception by Unquoted Path

Hijack Execution Flow: Services File Permissions Weakness

Hijack Execution Flow: Services Registry Permissions Weakness

Hijack Execution Flow: COR_PROFILER

Privilege Escalation

Select any Techniques used:

Boot or Logon Initialization Scripts

Boot or Logon Initialization Scripts: Logon Script (Windows)

Boot or Logon Initialization Scripts: Logon Script (Mac)

Boot or Logon Initialization Scripts: Network Logon Script

Boot or Logon Initialization Scripts: Rc.common

Boot or Logon Initialization Scripts: Startup Items

Scheduled Task/Job

Scheduled Task/Job: At (Linux)

Scheduled Task/Job: At (Windows)

Scheduled Task/Job: Cron

Scheduled Task/Job: Launchd

Scheduled Task/Job: Scheduled Task

Process Injection

Process Injection: Dynamic-link Library Injection

Process Injection: Portable Executable Injection

Process Injection: Thread Execution Hijacking

Process Injection: Asynchronous Procedure Call

Process Injection: Thread Local Storage

Process Injection: Ptrace System Calls

Process Injection: Proc Memory

Process Injection: Extra Window Memory Injection

Process Injection: Process Hollowing

Process Injection: Process Doppelgänging

Process Injection: VDSO Hijacking

Exploitation for Privilege Escalation

Valid Accounts

Valid Accounts: Default Accounts

Valid Accounts: Domain Accounts

Valid Accounts: Local Accounts

Valid Accounts: Cloud Accounts

Access Token Manipulation

Access Token Manipulation: Token Impersonation/Theft

Access Token Manipulation: Create Process with Token

Access Token Manipulation: Make and Impersonate Token

Access Token Manipulation: Parent PID Spoofing

Access Token Manipulation: SID-History Injection

Group Policy Modification

Create or Modify System Process

Create or Modify System Process: Launch Agent

Create or Modify System Process: Systemd Service

Create or Modify System Process: Windows Service

Create or Modify System Process: Launch Daemon

Event Triggered Execution

Event Triggered Execution: Change Default File Association

Event Triggered Execution: Screensaver

Event Triggered Execution: Windows Management Instrumentation Event Subscription

Event Triggered Execution: .bash_profile and .bashrc

Event Triggered Execution: Trap

Event Triggered Execution: LC_LOAD_DYLIB Addition

Event Triggered Execution: Netsh Helper DLL

Event Triggered Execution: Accessibility Features

Event Triggered Execution: AppCert DLLs

Event Triggered Execution: AppInit DLLs

Event Triggered Execution: Application Shimming

Event Triggered Execution: Image File Execution Options Injection

Event Triggered Execution: PowerShell Profile

Event Triggered Execution: Emond

Event Triggered Execution: Component Object Model Hijacking

Boot or Logon Autostart Execution

Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder

Boot or Logon Autostart Execution: Authentication Package

Boot or Logon Autostart Execution: Time Providers

Boot or Logon Autostart Execution: Winlogon Helper DLL

Boot or Logon Autostart Execution: Security Support Provider

Boot or Logon Autostart Execution: Kernel Modules and Extensions

Boot or Logon Autostart Execution: Re-opened Applications

Boot or Logon Autostart Execution: LSASS Driver

Boot or Logon Autostart Execution: Shortcut Modification

Boot or Logon Autostart Execution: Port Monitors

Boot or Logon Autostart Execution: Plist Modification

Abuse Elevation Control Mechanism

Abuse Elevation Control Mechanism: Setuid and Setgid

Abuse Elevation Control Mechanism: Bypass User Access Control

Abuse Elevation Control Mechanism: Sudo and Sudo Caching

Abuse Elevation Control Mechanism: Elevated Execution with Prompt

Hijack Execution Flow

Hijack Execution Flow: DLL Search Order Hijacking

Hijack Execution Flow: DLL Side-Loading

Hijack Execution Flow: Dylib Hijacking

Hijack Execution Flow: Executable Installer File Permissions Weakness

Hijack Execution Flow: LD_PRELOAD

Hijack Execution Flow: Path Interception by PATH Environment Variable

Hijack Execution Flow: Path Interception by Search Order Hijacking

Hijack Execution Flow: Path Interception by Unquoted Path

Hijack Execution Flow: Services File Permissions Weakness

Hijack Execution Flow: Services Registry Permissions Weakness

Hijack Execution Flow: COR_PROFILER

Topic Tags

Select the tags that apply to this CVE (Assessment added tags are disabled and cannot be removed)

What makes this of high-value to an attacker?

Vulnerable in default configuration

Unauthenticated

Observed in state-sponsored attacks

Observed in ransomware attacks

Gives privileged access

Easy to weaponize

Difficult to patch

Common in enterprise

CISA KEV Listed

What makes this of low-value to an attacker?

Vulnerable in uncommon configuration

Requires user interaction

Requires physical access

Requires elevated access

No useful access

Difficult to weaponize

Authenticated

Description

The MyBB Cross-Poster WordPress plugin is vulnerable to Stored Cross-Site Scripting due to insufficient input validation and sanitization via several parameters found in the ~/classes/MyBBXPSettings.php file which allowed attackers with administrative user access to inject arbitrary web scripts, in versions up to and including 1.0. This affects multi-site installations where unfiltered_html is disabled for administrators, and sites where unfiltered_html is disabled.

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Ratings & Analysis
Vulnerability Details

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CVSS V3 Severity and Metrics

Data provided by the National Vulnerability Database (NVD)

Base Score:

4.8 Medium

Impact Score:

2.7

Exploitability Score:

1.7

Vector:

CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

Attack Vector (AV):

Network

Attack Complexity (AC):

Low

Privileges Required (PR):

High

User Interaction (UI):

Required

Scope (S):

Changed

Confidentiality (C):

Low

Integrity (I):

Low

Availability (A):

None

General Information

Offensive Application

Unknown

Utility Class

Unknown

Ports

Unknown

Vulnerable Versions

MyBB Cross-Poster 1.0

Prerequisites

Unknown

Discovered By

Unknown

PoC Author

Unknown

Metasploit Module

Unknown

Reporter

Unknown

Vendors

mybb cross-poster project

Products

mybb cross-poster

Weaknesses

CWE-79

References

Canonical

CVE-2021-39338 (https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-39338)

Miscellaneous

https://www.wordfence.com/vulnerability-advisories/#CVE-2021-39338

https://github.com/BigTiger2020/word-press/blob/main/MyBB%20Cross-Poster.md

https://plugins.trac.wordpress.org/browser/mybb-cross-poster/trunk/classes/MyBBXPSettings.php

Additional Info

Authenticated

Unknown

Exploitable

Unknown

Reliability

Unknown

Stability

Unknown

Available Mitigations

Unknown

Shelf Life

Unknown

Userbase/Installbase

Unknown

Patch Effectiveness

Unknown

Rapid7

Technical Analysis

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Government or Industry Alert

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Threat Feed

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CVE ID

AttackerKB requires a CVE ID in order to pull vulnerability data and references from the CVE list and the National Vulnerability Database. If available, please supply below:

CVE ID:

Unknown

CVE-2021-39338

Unknown

Unknown

Required

High

Network

CVE-2021-39338

Description

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CVSS V3 Severity and Metrics

General Information

Vendors

Products

Weaknesses

References

Canonical

Miscellaneous

Additional Info

Technical Analysis

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