CVE-2026-39395

MEDIUM

Cosign's verify-blob-attestation reports false positive when payload parsing fails

Title source: cna

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.

References (1)

[X_Refsource_Confirm] https://github.com/sigstore/cosign/security/advisories/GHSA-w6c6-c85g-mmv6

Scores

CVSS v3 4.3

EPSS 0.0004

EPSS Percentile 11.3%

Attack Vector NETWORK

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

CISA SSVC

Vulnrichment

Exploitation none

Automatable no

Technical Impact partial

Details

CWE

CWE-754

Status published

Products (3)

sigstore/cosign < 2.6.3 (2 CPE variants)

sigstore/cosign 3.0.0 - 3.0.6Go

sigstore/cosign >= 3.0.0, < 3.0.6

Published Apr 07, 2026

Tracked Since Apr 08, 2026