CVE-2021-43860
Published: 12 January 2022
Summary
CVE-2021-43860 is a high-severity Improper Privilege Management (CWE-269) vulnerability in Debian Debian Linux. Its CVSS base score is 8.2 (High).
Operationally, ranked at the 37.4th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-30724
Vulnerability details
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…
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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.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Policy addresses roles, responsibilities, and privilege management to prevent improper privilege assignments.
Implements core proper privilege management by restricting to only required rights.
Baseline configuration documents and controls privilege assignments, making improper privilege management harder to introduce or sustain.
Requiring the most restrictive settings instead of defaults prevents incorrect default permissions on resources.
Defines roles and responsibilities to ensure proper privilege management during configuration changes.
Designates roles and review processes for managing physical privileges and access rights.
Tailoring explicitly overrides or scopes default permission assignments in the baseline to match the system's actual risk and operational needs.
Centralized privilege assignment and oversight prevent ad-hoc or excessive privilege grants that occur when each system is configured independently.