sigstore cosign up to 2.6.2/3.0.5 unusual condition

Summaryinfo

A vulnerability was found in sigstore cosign up to 2.6.2/3.0.5. It has been rated as problematic. Impacted is an unknown function. The manipulation leads to unusual condition. This vulnerability is listed as CVE-2026-39395. The attack may be initiated remotely. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in sigstore cosign up to 2.6.2/3.0.5. This issue affects an unknown function. The manipulation with an unknown input leads to a unusual condition vulnerability. Using CWE to declare the problem leads to CWE-754. The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product. Impacted is integrity. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-39395 since 04/07/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. It demands that the victim is doing some kind of user interaction. The technical details are unknown and an exploit is not publicly available.

Upgrading to version 2.6.3 or 3.0.6 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-19919). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

• sigstore

Name

• cosign

Version

• 2.6.0
• 2.6.1
• 2.6.2
• 3.0.0
• 3.0.1
• 3.0.2
• 3.0.3
• 3.0.4
• 3.0.5

Website

• Product: https://github.com/sigstore/cosign/

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Be aware that VulDB is the high quality source for vulnerability data.

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