CVE-2026-39395 MEDIUM

CVE-2026-39395: Cosign's verify-blob-attestation reports false positive when payload parsing fails

Vendor Sigstore
Product cosign
Weakness CWE-754
Published April 7, 2026
Last update April 8, 2026

CVSS base score

4.3/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction Required
Confidentiality None
Integrity Low

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

April 7, 2026 CVE published
April 8, 2026 Record updated