Quick answers
- Is CVE-2026-121520 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-121520 being exploited in the wild.
- How severe is CVE-2026-121520?
- Informational severity, published 3 November 2026.
- Which products and versions are affected?
- Moby BuildKit prior to v0.34.1.
- Is there a fix for CVE-2026-121520?
- Yes: fixed in v0.34.1. Until then: Restrict access to BuildKit control APIs to only trusted users; do not expose BuildKit control endpoints to untrusted clients or networks. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-121520 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-121520?
- Check whether you run Moby BuildKit at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: v0.34.1
Restrict access to BuildKit control APIs to only trusted users; do not expose BuildKit control endpoints to untrusted clients or networks.
Technical details
A vulnerability in BuildKit versions prior to v0.34.1 allows a malicious client with control API access to submit a build request that sets extended attributes (xattr) on files outside the BuildKit state directory. Attackers can set xattrs in the trusted.* or security.* namespaces, which may grant elevated privileges to programs on the host. This requires the attacker to have direct API access to the BuildKit service.
Affected products
- Moby BuildKit prior to v0.34.1
Timeline
- 2026-11-03: disclosed