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

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Summary

CVECVE-2026-39395
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-07 20:16:33 UTC
Updated2026-04-08 21:27:00 UTC
DescriptionCosign 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.

Risk And Classification

Primary CVSS: v3.1 4.3 MEDIUM from [email protected]

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

EPSS: 0.000290000 probability, percentile 0.082460000 (date 2026-04-09)

Problem Types: CWE-754 | CWE-754 CWE-754: Improper Check for Unusual or Exceptional Conditions

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary4.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
3.1CNADECLARED4.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Sigstore Cosign affected >= 3.0.0, < 3.0.6 Not specified
CNA Sigstore Cosign affected < 2.6.3 Not specified

References

ReferenceSourceLinkTags
github.com/sigstore/cosign/security/advisories/GHSA-w6c6-c85g-mmv6 [email protected] github.com
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