Medium severity · published Apr 7, 2026
CVE-2026-39395
Cosign's verify-blob-attestation reports false positive when payload parsing fails
5.3
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 15% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CO
cosign · sigstore
>= 3.0.0, < 3.0.6; < 2.6.3 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39395
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-39395
Mitigation
https://github.com/sigstore/cosign/security/advisories/GHSA-w6c6-c85g-mmv6
More from cosign
9.8
CVE-2022-35929
False positive signature verification in cosign
7.5
CVE-2024-29903
Cosign provides code signing and transparency for containers and binaries
5.9
CVE-2024-29902
Cosign provides code signing and transparency for containers and binaries
5.5
CVE-2026-22703
Cosign verification accepts any valid Rekor entry under certain conditions
5.5
CVE-2022-36056
Cosign is a project under the sigstore organization which aims to make signatures invisible infrastructure