CVE-2026-39395
Cosign's verify-blob-attestation reports false positive when payload parsing fails
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.
How to fix CVE-2026-39395
To remediate CVE-2026-39395, upgrade the affected package to a fixed version below.
- —upgrade to 2.6.3 or later
- —no fix listed
- —upgrade to 2.6.3-2 or later
- —upgrade to 3.0.6 or later
Is CVE-2026-39395 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (4)
- from 0, < 2.6.3, >= 3.0.0, < 3.0.6
- from 0
- from 0, < 2.6.3-2
- >= 3.0.0, < 3.0.6
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM4.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N |