CVE-2026-82331: Apache BuildStream: tar source extraction escape
- Is it exploited?
Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of . If CISA adds it, this page shows it as known exploited.
- How likely is exploitation in the next 30 days?
- 0.4%
EPSS score, percentile 35 of all scored records. A probability estimated by FIRST, not a report of exploitation.
- How severe?
- 9.8 Critical
CVSS v3.1 base score, from CISA's enrichment of the record
- What should I do?
CISA has set no required action, because the vulnerability is not in KEV.
- Which versions are affected?
Affected
- 2.8.0 and earlier
Unaffected 2.8.1
Source: CISA KEV 2026.10.29, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.
What to do
Advisories and patches
This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | 2.8.0 and earlier |
| Unaffected | 2.8.1 |
Versions not listed are: unaffected.
Versions the record lists as unaffected: 2.8.1.
Source: CVE List, as of . About the data.
About this vulnerability
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 sou…
Summary: CVE record, as of .
- CISA has not added CVE-2026-82331 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
- The CVE record was published on 23 Sep 2026.
- The CVE record carries a CVSS v3.1 base score of 9.8 (Critical), taken from CISA's enrichment of the record.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.4% (percentile 35), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
- CISA's SSVC assessment in the CVE record: exploitation none, automatable yes, technical impact total.
Source: CISA KEV 2026.10.29, as of ; CVE List, as of ; FIRST EPSS, as of . About the data.
Description
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 `tarfile` filter functionality, which blocks the symlink escape Users are recommended to upgrade to version 2.8.1, which fixes this issue.
Source: CVE List, as of . About the data.
Weakness
CWE-59
- CWE-59: Improper link resolution before file access ('link following')
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.
Timeline
| Date | Event |
|---|---|
| CVE record published |
Known exploited Apache vulnerabilities
- CVE-2016-3081: Apache Struts Command Injection Vulnerability
- CVE-2026-34486: Apache Tomcat Missing Encryption of Sensitive Data Vulnerability
- CVE-2026-34197: Apache ActiveMQ Improper Input Validation Vulnerability
- CVE-2024-38475: Apache HTTP Server Improper Escaping of Output Vulnerability
- CVE-2025-24813: Apache Tomcat Path Equivalence Vulnerability