Improper link resolution before file access ('link following') vulnerability in the tar source plugin of Apache BuildStream running on Python < 3.12… (CVE-2026-82331)
Description
A vulnerability in the tar source plugin of Apache BuildStream running on Python versions earlier than 3.12 allows malicious source tarballs to write files on the host system via symlink attacks. This can lead to arbitrary file writes with the privileges of the user running BuildStream. The issue is mitigated by using trusted sources, SHA256 hash pinning, and improvements in BuildStream 2.3.0 when running on Python 3.12 or later. Users are advised to upgrade to BuildStream version 2.8.1, which addresses this vulnerability.
CVSS v3.1
Score 9.8critical
Affected software
pkg:deb/ubuntu/buildstream?arch=source&distro=focalpkg:deb/ubuntu/buildstream?arch=source&distro=jammypkg:deb/ubuntu/buildstream?arch=source&distro=noblepkg:deb/ubuntu/buildstream?arch=source&distro=stonkingRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-82331 describes an improper link resolution vulnerability in the tar source plugin of Apache BuildStream when running on Python versions below 3.12. This flaw allows malicious tarballs to exploit symlink handling to write files on the host system with the privileges of the BuildStream user during source fetching. Mitigations include using trusted sources, SHA256 hash pinning to prevent MITM attacks, and the use of Python tarfile filter functionality in BuildStream 2.3.0 on Python 3.12 or later, which blocks symlink escapes. The issue is fixed in BuildStream version 2.8.1.
Potential Impact
Successful exploitation allows an attacker to write arbitrary files on the host system with the privileges of the user running BuildStream. This can lead to full compromise of the build environment and potentially the host system. The vulnerability has a high CVSS score of 9.8, indicating critical impact on confidentiality, integrity, and availability.
Mitigation Recommendations
Users should upgrade to BuildStream version 2.8.1, which fixes this vulnerability. Additionally, using trusted sources for BuildStream elements and relying on SHA256 hash pinning helps mitigate risk. Running BuildStream on Python 3.12 or later with BuildStream 2.3.0 or newer also provides protection by blocking symlink escapes via the Python tarfile filter functionality.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-82331
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:26.10"]
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ad3f5622cdf04f656661c6a
Added to database: 10/17/2026, 22:23:30 UTC
Last enriched: 10/17/2026, 23:32:07 UTC
Last updated: 10/17/2026, 23:32:07 UTC
Views: 2
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