sigstore cosign up to 3.0.4 Certificate Chain certificate validation

Summaryinfo

A vulnerability has been found in sigstore cosign up to 3.0.4 and classified as critical. Affected is an unknown function of the component Certificate Chain Handler. Performing a manipulation results in certificate validation. This vulnerability is cataloged as CVE-2026-24122. It is possible to initiate the attack remotely. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as problematic has been found in sigstore cosign up to 3.0.4. This affects an unknown part of the component Certificate Chain Handler. The manipulation with an unknown input leads to a certificate validation vulnerability. CWE is classifying the issue as CWE-295. The product does not validate, or incorrectly validates, a certificate. This is going to have an impact on integrity. The summary by CVE is:

Cosign provides code signing and transparency for containers and binaries. In versions 3.0.4 and below, an issuing certificate with a validity that expires before the leaf certificate will be considered valid during verification even if the provided timestamp would mean the issuing certificate should be considered expired. When verifying artifact signatures using a certificate, Cosign first verifies the certificate chain using the leaf certificate's "not before" timestamp and later checks expiry of the leaf certificate using either a signed timestamp provided by the Rekor transparency log or from a timestamp authority, or using the current time. The root and all issuing certificates are assumed to be valid during the leaf certificate's validity. There is no impact to users of the public Sigstore infrastructure. This may affect private deployments with customized PKIs. This issue has been fixed in version 3.0.5.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-24122 since 01/21/2026. The exploitability is told to be difficult. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1587.003 for this issue.

The vulnerability scanner Nessus provides a plugin with the ID 299730 (Linux Distros Unpatched Vulnerability : CVE-2026-24122), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 3.0.5 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 3c9a7363f563db76d78e2de2cabd945450f3781e is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (299730). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• sigstore

Name

• cosign

Version

• 3.0.0
• 3.0.1
• 3.0.2
• 3.0.3
• 3.0.4

License

• open-source

Website

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

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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