CVE-2026-39395
Medium
Description
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.
SeverityMedium
CVSS4.3
Exploit probability—
ProductSigstore Cosign
PublishedApr 7, 2026
First seenApr 7, 2026
Weakness typeCWE-754CWE-754
How to fix
Update
- sigstore cosign2.6.3, 3.0.6 or later
- github.com/sigstore/cosign3.0.6, 2.6.3 or later
- github.com/sigstore/cosign/v22.6.3 or later
- github.com/sigstore/cosign/v33.0.6 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| sigstore cosign | v < 2.6.3, 3.0.0 ≤ v < 3.0.6 | 2.6.3, 3.0.6 |
| github.com/sigstore/cosignGo | 3.0.0 ≤ v < 3.0.6, v < 2.6.3, No range specified | 3.0.6, 2.6.3 |
| github.com/sigstore/cosign/v2Go | v < 2.6.3 | 2.6.3 |
| github.com/sigstore/cosign/v3Go | 3.0.0 ≤ v < 3.0.6 | 3.0.6 |
Check your version
Choose the product and enter the version you run to see whether it falls in the affected range.
In the Intelligence 360 plan
Attack Surface Management
See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.