Symlink Attack Affecting github.com/moby/buildkit/vendor/github.com/tonistiigi/fsutil package, versions <0.34.1
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published12 Nov 2026
- disclosed3 Nov 2026
- creditcarlospinto4p
Introduced: 3 Nov 2026
NewCVE-2026-121520 Â (opens in a new tab)How to fix?
Upgrade github.com/moby/buildkit/vendor/github.com/tonistiigi/fsutil to version 0.34.1 or higher.
Overview
Affected versions of this package are vulnerable to Symlink Attack via the rewriteMetadata function in fsutil’s Unix file writer. A malicious client with access to BuildKit’s control API can send a build request that sets an xattr on a symlink, causing the xattr to be written to the symlink target outside the BuildKit state directory. This can include trusted. or security. xattrs that give a host program elevated privileges.
Workarounds
- Do not accept builds from untrusted users on affected BuildKit services; this prevents malicious clients from submitting requests that write xattrs outside the BuildKit state directory.