---
id: "CVE-2026-121520"
kind: "vulnerability"
aliases: ["CVE-2026-121520"]
title: "BuildKit: build requests can set extended attributes outside the state directory"
severity: "medium"
cvss: 4.5
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["buildkit", "ci", "docker", "infrastructure", "kubernetes"]
not_affected_if: ["trusted-clients-only"]
published_at: "2026-11-03T23:17:34+00:00"
first_seen_at: "2026-11-03T23:45:14+00:00"
updated_at: "2026-11-03T23:45:50+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121520", "first_seen_at": "2026-11-03T23:45:14+00:00"}]
---

# BuildKit: build requests can set extended attributes outside the state directory

A malicious client with access to BuildKit's control APIs can submit a build request that sets an extended attribute on a file outside the BuildKit state directory. Attributes in the trusted. or security. namespaces can also be set, which may give a host program elevated privileges.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the BuildKit version with `buildkitd --version` or `buildctl --version`
- Check whether build services accept build requests from untrusted users

## Fix

- BuildKit: move to `v0.34.1` or later

## Timeline

- 2026-11-03T23:45:14+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121520

## Documents

- [advisory] Vendor advisory: github.com https://github.com/moby/buildkit/security/advisories/GHSA-w26x-xg27-7qjc

## From the sources

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.

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