CVE-2026-93318: Cache poisoning via unvalidated image layer DiffIDs

Severity: high (CVSS 7.5 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-05 · updated 2026-10-06
Weakness: CWE-354

Description

A malicious image can advertise DiffIDs from another image while containing different layer contents. In affected versions, BuildKit could use the advertised DiffIDs to derive cache and snapshot identity without validating that they matched the actual layer contents. If a BuildKit daemon with shared or persistent cache first processes such a malicious image, a later build using the victim image may mount the attacker-controlled layer contents as the base image. This can allow code from the malicious image to run in the victim build, for example by replacing a commonly executed path such as /bin/sh. The attacker-controlled code may read build secrets mounted into the build, access other build resources, alter output artifacts, or hang the build. The issue affects both regular snapshotters and lazy-pulling snapshotters such as stargz.

Affected products

moby BuildKit: before 0.33.1 — fixed in 0.33.1

How to fix

Upgrade to a fixed version: moby BuildKit 0.33.1. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2026-93318 or the next vulnerability affects your stack