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  4. CVE 2026 121520 malicious client could set xattr value outside of
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Back to active CVEs
Medium · CVSS 4.5CVE-2026-121520

Malicious client could set xattr value outside of BuildKit state directoryCVE-2026-121520

Answer in brief

CVE-2026-121520 records a Medium severity (CVSS 4.5) vulnerability in Malicious client could set xattr value outside of BuildKit state directory. The current sources do not mark it as known exploited. The current feed maps Moby/BuildKit (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Nov 3, 2026Updated Nov 3, 2026Source checked Nov 3, 2026First seen by HOL Nov 3, 2026Material review Nov 3, 2026
Upstream Advisory

Key facts

Risk
Medium · CVSS 4.5
Exploitation
Not marked as known exploited
Affected software
1 mapped package or product
Fix availability
Available

Why this deserves its current priority

CVSS is 4.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Moby/BuildKit (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
Moby/BuildKitgeneric>=0 <0.34.10.34.1

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for Moby/BuildKit.
  2. 2Review the reported fix. Source-reported solution: Upgrade BuildKit to v0.34.1 or later.

Evidence timeline and material changes

  1. Published upstream

    Nov 3, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Nov 3, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Nov 3, 2026

Sources and claim methodology

  • GitHub security advisorygithub.com
Upstream source 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.

Quoted source text, attributed separately from HOL analysis.

Related CVEs

  • Possible panic from Git source resolverSame moby/buildkit package

Record context

Vulnerability class
Vulnerability
EPSS
Not reported
CWE IDs
CWE-61
Source
CVE List V5
Source checked
Nov 3, 2026
References
1 linked source
Open source record