CVE-2026-121520— Malicious client could set xattr value outside of BuildKit state directory

Quick assessment

Affected

Moby BuildKit

Exploitation

No confirmed in-the-wild exploitation; assess based on exposure

Recommended action

Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 BuildKit v0.34.1 之前的版本中，能够访问 BuildKit 控制 API 的恶意客户端可以提交构建请求，从而在 BuildKit 状态目录之外的文件上设置扩展属性（extended attribute）。此外，攻击者还可以设置属于或命名空间的扩展属性，这可能导致主机上的程序获得提升的特权。此问题影响那些接受来自不可信用户构建请求的构建服务。该问题已在 v0.34.1 版本中修复。

CVSS 4.5 · Medium Updated Nov 04, 2026

Possible ATT&CK Techniques 2 AI

T1548.001 · Setuid and Setgid T1190 · Exploit Public-Facing Application

Get alerts for future matching vulnerabilities Log in to subscribe

Vulnerability Information

Have questions about the vulnerability? See if Shenlong's analysis helps!

View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title

Malicious client could set xattr value outside of BuildKit state directory

Source: CVE Program / CVE List V5

Vulnerability 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.

Source: CVE Program / CVE List V5

CVSS Information

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

Source: CVE Program / CVE List V5

Vulnerability Type

CWE-61

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
Moby	BuildKit	0 ~ 0.34.1	-

II. Public POCs for CVE-2026-121520

#	POC Description	Source Link	Shenlong Link

AI-Generated POC Premium

No public POC found.

III. Intelligence Information for CVE-2026-121520

请登录查看更多情报信息。

Other References for CVE-2026-121520 (1)

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

https://www.cve.org/CVERecord?id=CVE-2026-121520

IV. Related Vulnerabilities

Same product: BuildKit

Same vendor: Moby

Same weakness: CWE-61