Attacker Value
Unknown
(0 users assessed)
Exploitability
Unknown
(0 users assessed)
User Interaction
Required
Privileges Required
None
Attack Vector
Local
0

CVE-2021-43860

Disclosure Date: January 12, 2022 •
CVE-2021-43860 CVSS v3 Base Score: 8.6
Add MITRE ATT&CK tactics and techniques that apply to this CVE.

Description

Flatpak is a Linux application sandboxing and distribution framework. Prior to versions 1.12.3 and 1.10.6, Flatpak doesn’t properly validate that the permissions displayed to the user for an app at install time match the actual permissions granted to the app at runtime, in the case that there’s a null byte in the metadata file of an app. Therefore apps can grant themselves permissions without the consent of the user. Flatpak shows permissions to the user during install by reading them from the “xa.metadata” key in the commit metadata. This cannot contain a null terminator, because it is an untrusted GVariant. Flatpak compares these permissions to the actual metadata, from the “metadata” file to ensure it wasn’t lied to. However, the actual metadata contents are loaded in several places where they are read as simple C-style strings. That means that, if the metadata file includes a null terminator, only the content of the file from before the terminator gets compared to xa.metadata. Thus, any permissions that appear in the metadata file after a null terminator are applied at runtime but not shown to the user. So maliciously crafted apps can give themselves hidden permissions. Users who have Flatpaks installed from untrusted sources are at risk in case the Flatpak has a maliciously crafted metadata file, either initially or in an update. This issue is patched in versions 1.12.3 and 1.10.6. As a workaround, users can manually check the permissions of installed apps by checking the metadata file or the xa.metadata key on the commit metadata.

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CVSS V3 Severity and Metrics
Base Score:
8.6 High
Impact Score:
6
Exploitability Score:
1.8
Vector:
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Attack Vector (AV):
Local
Attack Complexity (AC):
Low
Privileges Required (PR):
None
User Interaction (UI):
Required
Scope (S):
Changed
Confidentiality (C):
High
Integrity (I):
High
Availability (A):
High

General Information

Offensive Application
Unknown
Utility Class
Unknown
Ports
Unknown
OS
Unknown
Vulnerable Versions
flatpak >= 1.11.0, < 1.12.3
flatpak < 1.10.6
Prerequisites
Unknown
Discovered By
Unknown
PoC Author
Unknown
Metasploit Module
Unknown
Reporter
Unknown

Vendors

  • debian,
  • fedoraproject,
  • flatpak,
  • redhat

Products

  • debian linux 10.0,
  • debian linux 11.0,
  • debian linux 9.0,
  • enterprise linux 8.0,
  • fedora 35,
  • flatpak
Technical Analysis