CVE-2021-43860: Permissions granted to applications can be hidden from the user at install time
First published: Wed Jan 12 2022(Updated: )
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.
Credit: security-advisories@github.com security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| <1.10.6 | ||
| >=1.11.1<=1.12.3 | ||
| =35 | ||
| =8.0 | ||
| =9.0 | ||
| =10.0 | ||
| =11.0 | ||
| Flatpak Flatpak | <1.10.6 | |
| Flatpak Flatpak | >=1.11.1<=1.12.3 | |
| Fedoraproject Fedora | =35 | |
| Redhat Enterprise Linux | =8.0 | |
| Debian Debian Linux | =9.0 | |
| Debian Debian Linux | =10.0 | |
| Debian Debian Linux | =11.0 | |
| debian/flatpak | <=1.2.5-0+deb10u4 | 1.10.8-0+deb11u1 1.10.7-0+deb11u1 1.14.4-1 1.14.5-1 |
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Reference Links
- https://github.com/flatpak/flatpak/security/advisories/GHSA-qpjc-vq3c-572j
- https://github.com/flatpak/flatpak/commit/54ec1a482dfc668127eaae57f135e6a8e0bc52da
- https://github.com/flatpak/flatpak/commit/65cbfac982cb1c83993a9e19aa424daee8e9f042
- https://github.com/flatpak/flatpak/commit/93357d357119093804df05acc32ff335839c6451
- https://github.com/flatpak/flatpak/commit/ba818f504c926baaf6e362be8159cfacf994310e
- https://github.com/flatpak/flatpak/commit/d9a8f9d8ccc0b7c1135d0ecde006a75d25f66aee
- https://github.com/flatpak/flatpak/releases/tag/1.10.6
- https://github.com/flatpak/flatpak/releases/tag/1.12.3
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/APFTBYGJJVJPFVHRXUW5PII5XOAFI4KH/
- https://www.debian.org/security/2022/dsa-5049
- https://security.gentoo.org/glsa/202312-12
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/APFTBYGJJVJPFVHRXUW5PII5XOAFI4KH/
- https://security-tracker.debian.org/tracker/CVE-2021-43860
Frequently Asked Questions
What is CVE-2021-43860?
CVE-2021-43860 is a vulnerability in the Flatpak Linux application sandboxing and distribution framework.
What is the severity of CVE-2021-43860?
CVE-2021-43860 has a severity rating of 8.6 (high).
How does CVE-2021-43860 affect Flatpak installations?
CVE-2021-43860 affects Flatpak versions 1.12.3 and 1.10.6, where it doesn't properly validate permissions during installation.
Are there any fixes available for CVE-2021-43860?
Yes, fixes are available for CVE-2021-43860. Users should update to Flatpak versions 1.12.3 or 1.10.8.
What are the references for CVE-2021-43860?
The references for CVE-2021-43860 can be found at the following links: [reference 1](https://github.com/flatpak/flatpak/commit/54ec1a482dfc668127eaae57f135e6a8e0bc52da), [reference 2](https://github.com/flatpak/flatpak/commit/65cbfac982cb1c83993a9e19aa424daee8e9f042), [reference 3](https://github.com/flatpak/flatpak/commit/93357d357119093804df05acc32ff335839c6451).
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