CVE-2026-82331 Apache BuildStream: tar source extraction escape
Malicious tarballs can write files to the host via symlink escapes during source fetching, potentially leading to code execution or data modification.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-82331?
CVE-2026-82331 is a critical path traversal vulnerability in Apache BuildStream, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Improper link resolution before file access ('link following') vulnerability in the `tar` source plugin of Apache BuildStream running on Python < 3.12 allows malicious source tarballs to write files on the host, with the privileges of the user running BuildStream, via symlinks as part of source fetching. The impact of this issue is mitigated by:
* BuildStream projects should only use trusted sources in their elements as otherwise the build output can also not be trusted * Tracking a source tarball pins its SHA256 hash, which prevents MITM attacks of users that are fetching an already tracked project * When running on Python >= 3.12, BuildStream >= 2.3.0 already makes use of the Python `tarfile` filter functionality, which blocks the symlink escape
Users are recommended to upgrade to version 2.8.1, which fixes this issue.
Weakness: CWE-59
Which versions are affected by CVE-2026-82331?
How do I fix CVE-2026-82331?
Upgrade to a fixed version.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-82331 being exploited?
There is no known exploitation of CVE-2026-82331 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-82331, GHSA-5xjv-h9hc-3vv9, UBUNTU-CVE-2026-82331.