CVE-2026-121520
Malicious client could set xattr value outside of BuildKit state directory
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.
INFO
Published Date :
Nov. 3, 2026, 11:17 p.m.
Last Modified :
Nov. 3, 2026, 11:17 p.m.
Remotely Exploit :
No
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | MEDIUM | 686469e6-3ff6-451b-ab8b-cf5b9e89401e | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update BuildKit to version v0.34.1 or later.
- Restrict access to BuildKit control APIs.
- Validate build requests from untrusted users.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-121520.
| URL | Resource |
|---|---|
| https://github.com/moby/buildkit/security/advisories/GHSA-w26x-xg27-7qjc |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-121520 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-121520
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-121520 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-121520 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Nov. 03, 2026
Action Type Old Value New Value Added 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. Added CVSS V4.0 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 Added CWE CWE-61 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/121xxx/CVE-2026-121520.json">CVE-2026-121520</a> Added Reference https://github.com/moby/buildkit/security/advisories/GHSA-w26x-xg27-7qjc