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Vulnerability · Published Sep 23, 2026 · Assigned by apache

CVE-2026-82331Apache BuildStream: tar source extraction escape

Critical 9.8

In plain English

A critical-severity security flaw in Apache BuildStream from Apache Software Foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 35% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)9.8Critical
Exploit odds (30 days)0.4%top 64.7% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12buildstreamno fix listedDEBIAN-CVE-2026-82331
Debian:13buildstream1.6.9-2+deb13u1DEBIAN-CVE-2026-82331
Debian:14buildstream2.8.1-1DEBIAN-CVE-2026-82331
Ubuntu:22.04:LTSbuildstreamno fix listedUBUNTU-CVE-2026-82331
Ubuntu:24.04:LTSbuildstreamno fix listedUBUNTU-CVE-2026-82331
Ubuntu:26.10buildstreamno fix listedUBUNTU-CVE-2026-82331

Affected products (as reported)

VendorProductVersions
Apache Software Foundation Apache BuildStream 0 – through 2.8.0

Weakness: CWE-59 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References