CVE-2026-82331
Apache BuildStream: tar source extraction escape
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
tarfilefilter functionality, which blocks the symlink escape
Users are recommended to upgrade to version 2.8.1, which fixes this issue.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Apache BuildStream: tar source extraction escape
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
tarfilefilter functionality, which blocks the symlink escape
Users are recommended to upgrade to version 2.8.1, which fixes this issue.
- Record
CVE-2026-82331- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-59
- Updated
- 2026-11-02
EUVDEUVD-2026-85113
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
tarfilefilter functionality, which blocks the symlink escape
Users are recommended to upgrade to version 2.8.1, which fixes this issue.
- Record
EUVD-2026-85113- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-5xjv-h9hc-3vv9
Improper link resolution before file access ('link following') vulnerability in the `tar` source...
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
tarfilefilter functionality, which blocks the symlink escape
Users are recommended to upgrade to version 2.8.1, which fixes this issue.
- Record
GHSA-5xjv-h9hc-3vv9- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-59
- Updated
- 2026-11-02
NVD
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
tarfilefilter functionality, which blocks the symlink escape
Users are recommended to upgrade to version 2.8.1, which fixes this issue.
- Record
CVE-2026-82331- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-59
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-82331
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.
- Record
DEBIAN-CVE-2026-82331- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-82331
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.
- Record
UBUNTU-CVE-2026-82331- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
buildstreamDebian:12 | All versions, plus listed versions 1.6.8-21.6.9-11.6.9-1.11.6.9-21.6.9-3 Show 5 moreShow less2.7.0-12.7.0-22.7.0-32.8.0-12.8.1-1 | None known |
buildstreamDebian:13 | before 1.6.9-2+deb13u1, plus listed versions 1.6.9-2 | 1.6.9-2+deb13u1 |
buildstreamDebian:14 | before 2.8.1-1, plus listed versions 1.6.9-21.6.9-32.7.0-12.7.0-22.7.0-32.8.0-1 | 2.8.1-1 |
buildstreamUbuntu:20.04:LTS | All versions, plus listed versions 1.4.1-1 | None known |
buildstreamUbuntu:22.04:LTS | All versions, plus listed versions 1.6.1-1 | None known |
buildstreamUbuntu:24.04:LTS | All versions, plus listed versions 1.6.9-1 | None known |
buildstreamUbuntu:26.10 | All versions, plus listed versions 2.7.0-32.8.0-12.8.1-1 | None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-82331 is a critical vulnerability (CVSS 9.8) in Apache Software Foundation Buildstream, published September 23, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.41%, the 35th percentile. Fixed in buildstream 1.6.9-2+deb13u1.