sigstore/cosign · Security
Cosign's verify-blob-attestation reports false positive when payload parsing fails
- GHSA ID
- GHSA-w6c6-c85g-mmv6
- CVE ID
- CVE-2026-39395
- Severity
- medium
- Published
- Updated
- CVSS
- 4.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
- CVSS v3
- 4.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
Description
Description
cosign verify-blob-attestation may erroneously report a "Verified OK" result for attestations with malformed payloads or mismatched predicate types. For old-format bundles and detached signatures, this was due to a logic flaw in the error handling of the predicate type validation. For new-format bundles, the predicate type validation was bypassed completely.
Impact
When cosign verify-blob-attestation is used without --check-claims set to true, an attestation that has a valid signature but a malformed or unparsable payload would be incorrectly validated. Additionally, systems relying on --type <predicate type> to reject attestations with mismatched types would be lead to trust the unexpected attestation type.
Patches
v3.0.6, v2.6.3
Workarounds
Always set --check-claims=true for attestation verification.
CWEs
- CWE-754 · Improper Check for Unusual or Exceptional Conditions