Malicious client could set xattr value outside of BuildKit state directory

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-121520
StatePUBLISHED
AssignerDocker
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-03 23:17:34 UTC
Updated2026-11-03 23:17:34 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v4.0 4.5 MEDIUM from [email protected]

CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Problem Types: CWE-61 | CWE-61 CWE-61: UNIX Symbolic Link (Symlink) Following

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary4.5MEDIUMCVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:H/E:X/C...
4.0CNACVSS4.5MEDIUMCVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:H

CVSS v4.0 Breakdown

Attack Vector
Local
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
High
User Interaction
None
Confidentiality
None
Integrity
None
Availability
None
Sub Conf.
None
Sub Integrity
High
Sub Availability
High

CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Moby BuildKit affected 0.34.1 semver Not specified

References

ReferenceSourceLinkTags
github.com/moby/buildkit/security/advisories/GHSA-w26x-xg27-7qjc [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

Solutions

CNA: Upgrade BuildKit to v0.34.1 or later.

Workarounds

CNA: Restrict access to BuildKit control APIs to trusted clients and do not accept build requests from untrusted users.

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