medium4.3
CVE-2026-39395
Cosign's verify-blob-attestation reports false positive when payload parsing fails
Impact
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 packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| go | github.com/sigstore/cosign | >= 3.0.0, < 3.0.6 | 3.0.6 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Sigstore | Cosign | before 2.6.3 from 3.0.0 before 3.0.6 |