Attacker Value
Moderate
(1 user assessed)
Exploitability
Moderate
(1 user assessed)
User Interaction
Required
Privileges Required
None
Attack Vector
Network
1

CVE-2021-26419

Disclosure Date: May 11, 2021
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Initial Access
Techniques
Validation
Validated

Description

Scripting Engine Memory Corruption Vulnerability

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2
Ratings
  • Attacker Value
    Medium
  • Exploitability
    Medium
Technical Analysis

Details

The vulnerability affects Internet Explorer 11 on all Windows Versions. It is located in the jscript9.dll library, which is used to execute javascript.

Possible attack vectors:

  • website content
  • activeX components in office documents

Google Project Zero released a PoC on 13.05.2021, which triggers the vulnerability and causes a crash. At the time of writing I could not find any weaponized exploit.

The CVSS rating of the vulnerability differs between Windows desktop versions and server versions. In server versions the CVSS Privileges Required is set to High. Desktop versions are rated with CVSS None. The reason could be, that IE enhanced protection mode is disabled on Windows desktop versions and enabled on server versions by default.

Rating explanation

My rating of the exploitability score was affected by the availability of the PoC and the Microsoft exploitability rating. In year 2020, Operation PowerFall was using a similar vulnerability (CVE-2020-1380) in IE. I expect to see exploits for CVE-2021-26419 in a similar context.

Attackers might gain direct control over the host after exploitation without a sandbox escape. IE 11 does have a enhanced protected mode (EPM), which runs IE in an AppContainer and acts as a sandbox. EPM was introduced with Windows 8 and is disabled by default on Windows desktop versions.

Sources

CVSS V3 Severity and Metrics
Base Score:
7.5 High
Impact Score:
5.9
Exploitability Score:
1.6
Vector:
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Attack Vector (AV):
Network
Attack Complexity (AC):
High
Privileges Required (PR):
None
User Interaction (UI):
Required
Scope (S):
Unchanged
Confidentiality (C):
High
Integrity (I):
High
Availability (A):
High

General Information

Vendors

  • Microsoft

Products

  • Internet Explorer 11,
  • Internet Explorer 9,
  • Internet Explorer 11 on Windows 10 Version 1909 for 32-bit Systems,
  • Internet Explorer 11 on Windows 10 Version 1909 for x64-based Systems,
  • Internet Explorer 11 on Windows 10 Version 1909 for ARM64-based Systems,
  • Internet Explorer 11 on Windows 10 Version 2004 for 32-bit Systems,
  • Internet Explorer 11 on Windows 10 Version 2004 for ARM64-based Systems,
  • Internet Explorer 11 on Windows 10 Version 2004 for x64-based Systems,
  • Internet Explorer 11 on Windows 10 Version 20H2 for x64-based Systems,
  • Internet Explorer 11 on Windows 10 Version 20H2 for 32-bit Systems,
  • Internet Explorer 11 on Windows 10 Version 20H2 for ARM64-based Systems,
  • Internet Explorer 11 on Windows Server 2012

Additional Info

Technical Analysis