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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Fixes

Solution

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Workaround

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History

Wed, 23 Sep 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Wed, 23 Sep 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}


Wed, 23 Sep 2026 11:45:00 +0000

Type Values Removed Values Added
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.
Title Apache BuildStream: tar source extraction escape
Weaknesses CWE-59
References

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cve-icon MITRE

Status: PUBLISHED

Assigner: apache

Published:

Updated: 2026-09-23T16:08:58.171Z

Reserved: 2026-08-28T14:59:00.996Z

Link: CVE-2026-82331

cve-icon Vulnrichment

Updated: 2026-09-23T14:55:51.225Z

cve-icon NVD

Status : Received

Published: 2026-09-23T07:16:46.493

Modified: 2026-09-23T15:17:22.520

Link: CVE-2026-82331

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-23T15:15:05Z

Weaknesses