CVE-2026-39395: Sigstore Cosign

Medium severity, CVSS 5.3. EPSS: 0.3% chance of exploitation in the next 30 days.

Cosign provides code signing and transparency for containers and binaries. Prior to 3.0.6 and 2.6.3, 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. This vulnerability is fixed in 3.0.6 and 2.6.3.

Affected products

• Sigstore Cosign: before 2.6.3 (fixed in 2.6.3); from 3.0.0, before 3.0.6 (fixed in 3.0.6)

Published 2026-04-07. Last modified 2026-07-24.