Bug 2539099 (CVE-2026-82331) - CVE-2026-82331 buildstream: Apache BuildStream: Arbitrary file write via symlinks in tar source plugin
Summary: CVE-2026-82331 buildstream: Apache BuildStream: Arbitrary file write via syml...
Keywords:
Status: NEW
Alias: CVE-2026-82331
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
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Depends On: 2542448 2542449
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-09-23 07:12 UTC by OSIDB Bzimport
Modified: 2026-09-28 12:46 UTC (History)
0 users

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Description OSIDB Bzimport 2026-09-23 07:12:03 UTC 
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.
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