CVE-2026-93318

Summary

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 Software

VendorProductVersion RangeStatus
mobyBuildKit0 < 0.33.1affected

Weaknesses

  • CWE-354: CWE-354: Improper Validation of Integrity Check Value

Workarounds

Do not share BuildKit daemon cache between trusted and untrusted builds. Use isolated BuildKit daemons or ephemeral builders for untrusted image sources, or prune BuildKit cache after processing untrusted images.

Disabling stargz alone is not sufficient because regular snapshotters are also affected.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: total

References