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

CVE-2021-21381

Disclosure Date: March 11, 2021
Add MITRE ATT&CK tactics and techniques that apply to this CVE.

Description

Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. In Flatpack since version 0.9.4 and before version 1.10.2 has a vulnerability in the “file forwarding” feature which can be used by an attacker to gain access to files that would not ordinarily be allowed by the app’s permissions. By putting the special tokens @@ and/or @@u in the Exec field of a Flatpak app’s .desktop file, a malicious app publisher can trick flatpak into behaving as though the user had chosen to open a target file with their Flatpak app, which automatically makes that file available to the Flatpak app. This is fixed in version 1.10.2. A minimal solution is the first commit “Disallow @@ and @@U usage in desktop files”. The follow-up commits “dir: Reserve the whole @@ prefix” and “dir: Refuse to export .desktop files with suspicious uses of @@ tokens” are recommended, but not strictly required. As a workaround, avoid installing Flatpak apps from untrusted sources, or check the contents of the exported .desktop files in exports/share/applications/*.desktop (typically ~/.local/share/flatpak/exports/share/applications/*.desktop and /var/lib/flatpak/exports/share/applications/*.desktop) to make sure that literal filenames do not follow @@ or @@u.

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CVSS V3 Severity and Metrics
Base Score:
8.2 High
Impact Score:
5.8
Exploitability Score:
1.8
Vector:
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
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):
None

General Information

Vendors

  • debian,
  • fedoraproject,
  • flatpak

Products

  • debian linux 10.0,
  • fedora 33,
  • fedora 34,
  • flatpak
Technical Analysis