# CVE-2026-121520: Malicious client could set xattr value outside of BuildKit state directory

> CVE-2026-121520: Malicious client could set xattr value outside of BuildKit state directory. CVSS 4.5 (CVSS 4.0).

Canonical: https://rewindex.com/cve/CVE-2026-121520
Last updated: 2026-11-03T23:17:34Z

- Published: 2026-11-03 22:11 UTC · Updated: 2026-11-03 23:17 UTC · Assigner: Docker
- CVSS: 4.5 (CVSS 4.0) · Severity: Medium
- EPSS: 0.14%, 3th percentile (scored 2026-11-04)
- CISA KEV: no
- CWE: CWE-61

## Description

In BuildKit versions prior to v0.34.1, a malicious client with access to the BuildKit control APIs can submit a build request that sets an extended attribute on a file outside the BuildKit state directory. Extended attributes in the trusted. or security. namespaces may also be set, potentially giving a program on the host elevated privileges. This issue affects build services that accept build requests from untrusted users. The issue is fixed in v0.34.1.

## Affected vendors and products

- Moby: BuildKit

## Tracked companies

- [Docker](https://rewindex.com/company/docker.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-121520)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-121520)
- [https://github.com/moby/buildkit/security/advisories/GHSA-w26x-xg27-7qjc](https://github.com/moby/buildkit/security/advisories/GHSA-w26x-xg27-7qjc)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-121520 · Markdown: https://rewindex.com/cve/CVE-2026-121520.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-121520 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-11-05T10:25:27.098Z