CVE-2026-39395: CWE-754: Improper Check for Unusual or Exceptional Conditions in sigstore cosign
Cosign versions prior to 3.0.6 and 2.6.3 contain a vulnerability where the verify-blob-attestation command may incorrectly report a successful verification for attestations with malformed payloads or mismatched predicate types. This occurs due to improper error handling and bypass of predicate type validation in different bundle formats. The issue is fixed in versions 3.0.6 and 2.6.
AI Analysis
Technical Summary
The vulnerability in sigstore's cosign affects the verify-blob-attestation functionality, where malformed or mismatched attestation payloads can be erroneously accepted as valid. For old-format bundles and detached signatures, a logic flaw in error handling caused this incorrect verification. For new-format bundles, predicate type validation was completely bypassed. This improper check for unusual or exceptional conditions (CWE-754) could lead to false positive verification results. The flaw is resolved in cosign versions 3.0.6 and 2.6.3.
Potential Impact
The vulnerability may cause cosign to incorrectly verify attestations that have malformed payloads or mismatched predicate types, potentially undermining the integrity of the verification process. There is no impact on confidentiality or availability. No known exploits are reported in the wild.
Mitigation Recommendations
Upgrade cosign to version 3.0.6 or later, or 2.6.3 or later, where this vulnerability is fixed. Patch status is confirmed by the version information in the advisory. No additional mitigation is indicated.
CVE-2026-39395: CWE-754: Improper Check for Unusual or Exceptional Conditions in sigstore cosign
Description
Cosign versions prior to 3.0.6 and 2.6.3 contain a vulnerability where the verify-blob-attestation command may incorrectly report a successful verification for attestations with malformed payloads or mismatched predicate types. This occurs due to improper error handling and bypass of predicate type validation in different bundle formats. The issue is fixed in versions 3.0.6 and 2.6.
CVSS v3.1
Score 4.3medium
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in sigstore's cosign affects the verify-blob-attestation functionality, where malformed or mismatched attestation payloads can be erroneously accepted as valid. For old-format bundles and detached signatures, a logic flaw in error handling caused this incorrect verification. For new-format bundles, predicate type validation was completely bypassed. This improper check for unusual or exceptional conditions (CWE-754) could lead to false positive verification results. The flaw is resolved in cosign versions 3.0.6 and 2.6.3.
Potential Impact
The vulnerability may cause cosign to incorrectly verify attestations that have malformed payloads or mismatched predicate types, potentially undermining the integrity of the verification process. There is no impact on confidentiality or availability. No known exploits are reported in the wild.
Mitigation Recommendations
Upgrade cosign to version 3.0.6 or later, or 2.6.3 or later, where this vulnerability is fixed. Patch status is confirmed by the version information in the advisory. No additional mitigation is indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-04-06T22:06:40.516Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69d5660baaed68159a5b407a
Added to database: 04/07/2026, 20:16:11 UTC
Last enriched: 04/15/2026, 15:54:40 UTC
Last updated: 07/31/2026, 19:22:58 UTC
Views: 236
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