# CVE-2026-82331: buildstream: Improper link resolution before file access ('link following') vulnerability in the `tar` source plugin of Apache Bui...

CVE-2026-82331 is fixed in buildstream on 1 platform, first by DEBIAN-CVE-2026-82331, released September 26, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-82331
- Priority: Urgent
- CVSS: 9.8 (critical)
- EPSS: 0.0041
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 23, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | buildstream Debian 13.5 (trixie) | 1.6.9-2+deb13u1 | [DEBIAN-CVE-2026-82331](https://patchblox.com/security/data/fix/linux/debian-cve-2026-82331.md) | Sep 26, 2026 |
| Linux | buildstream Debian 14 | 2.8.1-1 | [DEBIAN-CVE-2026-82331](https://patchblox.com/security/data/fix/linux/debian-cve-2026-82331.md) | Sep 26, 2026 |

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Data as of 2026-11-09T19:38:12Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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