Cosign considered signatures valid with expired intermediate certificates when transparency log verification is skipped

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

3.7 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS

• CVE-2026-24122: 0.21% estimated exploitation activity in the next 30 days; percentile 12.01 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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. 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. Impact No impact to users of the public Sigstore infrastructure. This may affect private deployments with customized PKIs. In practice, this is unlikely to occur as CAs should not be issuing certificates that outlive the validity of the CA and its parents. Workarounds Upgrade to the latest release, or verify the certificate chain out of…

Published by the source

19 Feb 2026, 22:09 UTC

Last modified by the source

20 Feb 2026, 16:43 UTC

Source last checked

26 Oct 2026, 15:14 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-wfqv-66vq-46rm

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# Patch Next advisory brief: CVE-2026-24122

Advisory: Cosign considered signatures valid with expired intermediate certificates when transparency log verification is skipped
IDs: CVE-2026-24122, GHSA-wfqv-66vq-46rm
Record: https://patchnext.com/advisories/cve-2026-24122 (revision 1, source checked 26 Oct 2026, 15:14 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/sigstore/cosign 3.0.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/sigstore/cosign: affected <= 3.0.4; fixed in 3.0.5

## Suggested inspection (read-only)
- Go github.com/sigstore/cosign: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/sigstore/cosign.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-wfqv-66vq-46rm (GitHub-reviewed advisory GHSA-wfqv-66vq-46rm lists affected ranges: Go github.com/sigstore/cosign >=0 <=3.0.4)

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