Vulnerability · Published Jan 14, 2021 · Assigned by GitHub_M
CVE-2021-21261Flatpak sandbox escape via spawn portal
High 7.3
In plain English
A high-severity injection in flatpak from flatpak. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 49% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. A bug was discovered in the `flatpak-portal` service that can allow sandboxed applications to execute arbitrary code on the host system (a sandbox escape). This sandbox-escape bug is present in versions from 0.11.4 and before fixed versions 1.8.5 and 1.10.0. The Flatpak portal D-Bus service (`flatpak-portal`, also known by its D-Bus service name `org.freedesktop.portal.Flatpak`) allows apps in a Flatpak sandbox to launch their own subprocesses in a new sandbox instance, either with the same security settings as the caller or with more restrictive security settings. For example, this is used in Flatpak-packaged web browsers such as Chromium to launch subprocesses that will process untrusted web content, and give those subprocesses a more restrictive sandbox than the browser itself. In vulnerable versions, the Flatpak portal service passes caller-specified environment variables to non-sandboxed processes on the host system, and in particular to the `flatpak run` command that is used to launch the new sandbox instance. A malicious or compromised Flatpak app could set environment variables that are trusted by the `flatpak run` command, and use them to execute arbitrary code that is not in a sandbox. As a workaround, this vulnerability can be mitigated by preventing the `flatpak-portal` service from starting, but that mitigation will prevent many Flatpak apps from working correctly. This is fixed in versions 1.8.5 and 1.10.0.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.20 | flatpak | 1.10.1-r0 | ALPINE-CVE-2021-21261 |
| Alpine:v3.21 | flatpak | 1.10.1-r0 | ALPINE-CVE-2021-21261 |
| Alpine:v3.22 | flatpak | 1.10.1-r0 | ALPINE-CVE-2021-21261 |
| Alpine:v3.23 | flatpak | 1.10.1-r0 | ALPINE-CVE-2021-21261 |
| Alpine:v3.24 | flatpak | 1.10.1-r0 | ALPINE-CVE-2021-21261 |
| Debian:12 | flatpak | 1.8.5-1 | DEBIAN-CVE-2021-21261 |
| Debian:13 | flatpak | 1.8.5-1 | DEBIAN-CVE-2021-21261 |
| Debian:14 | flatpak | 1.8.5-1 | DEBIAN-CVE-2021-21261 |
Affected products (as reported)
Weakness: CWE-74 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
References
- https://github.com/flatpak/flatpak/security/advisories/GHSA-4ppf-fxf6-vxg2 x_refsource_CONFIRM
- https://github.com/flatpak/flatpak/releases/tag/1.8.5 x_refsource_MISC
- DSA-4830 vendor-advisory, x_refsource_DEBIAN
- https://github.com/flatpak/flatpak/commit/6d1773d2a54dde9b099043f07a2094a4f1c2f486 x_refsource_MISC
- https://github.com/flatpak/flatpak/commit/6e5ae7a109cdfa9735ea7ccbd8cb79f9e8d3ae8b x_refsource_MISC
- https://github.com/flatpak/flatpak/commit/aeb6a7ab0abaac4a8f4ad98b3df476d9de6b8bd4 x_refsource_MISC
- https://github.com/flatpak/flatpak/commit/cc1401043c075268ecc652eac557ef8076b5eaba x_refsource_MISC
- GLSA-202101-21 vendor-advisory, x_refsource_GENTOO