CVE-2026-121520

Malicious client could set xattr value outside of BuildKit state directory

publishedCWE-61

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.

Technical severity4.5 mediumCVSS 4.0 · CNA: Docker

Published2026-11-03Source updated 2026-11-06

Collected2026-11-073 attributed sources

Fixes and workarounds

Fix

Upgrade BuildKit to v0.34.1 or later.

Source: CNA: Docker

Workaround

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

Source: CNA: Docker

Affected products and versions

Affected products, source version ranges and reporting authorities
Product	Versions	Authority
BuildKit Moby	≥ 0; < 0.34.1 (affected, semver) Other versions: unaffected	CNA: Docker

Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.

CVSS assessments

CVSS scores, vectors and reporting authorities
Version / score	Vector	Authority
4.0 / 4.5 medium	`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`	CNA: Docker
4.0 / 4.5 medium	`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`	NVD: [email protected]

Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

References

https://github.com/moby/buildkit/security/advisories/GHSA-w26x-xg27-7qjcCNA: Docker · vendor-advisory
https://github.com/moby/buildkit/security/advisories/GHSA-w26x-xg27-7qjc[email protected]

For agents and automation

Read public disclosures for free as Markdown or JSON. Compatible browsers also expose native WebMCP tools to search disclosures, read this page, and discover API access.

Use the ontology-linked Cyber API with x402 pay per request, or a Y2 Pro or Elite API key with the intel:cyber scope.

Get an API key Use x402 Connect an agent

Endpoints and access details

https://api.y2.dev/api/v2/cyber/cves
https://api.y2.dev/api/v2/cyber/cves/{cveId}

A workspace owner or admin can create a Pro or Elite API key. Send Authorization: Bearer <Y2_API_KEY> from your trusted agent runtime.

For x402, omit Authorization and read the HTTP 402 payment challenge before signing a retry. Public browser tools do not make payments.

Agent access JSON · OpenAPI · CVE API guide