sigstore-ruby verifier returns success for DSSE bundles with mismatched in-toto subject digest

Exploitation

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

CVSS

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

EPSS

• CVE-2026-31830: 0.25% estimated exploitation activity in the next 30 days; percentile 16.78 (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 Sigstore::Verifier#verify does not propagate the VerificationFailure returned by verifyintoto when the artifact digest does not match the digest in the in-toto attestation subject. As a result, verification of DSSE bundles containing in-toto statements returns VerificationSuccess regardless of whether the artifact matches the attested subject. Details In lib/sigstore/verifier.rb, the verify method calls verifyintoto (line 176) without capturing or checking its return value: verifyintoto(input, intoto) When verifyintoto detects a digest mismatch, it returns a VerificationFailure object. Because the caller discards this return value, execution unconditionally falls through to return VerificationSuccess. This is the only verification sub-check in the method (out of 12) whose failure is not propagated. The messagesignature code path is not affected. Impact An attacker who possesses a valid signed DSSE bundle containing an in-toto attestation for artifact A can present it as a…

Published by the source

11 Mar 2026, 00:24 UTC

Last modified by the source

19 Mar 2026, 21:02 UTC

Source last checked

26 Oct 2026, 15:51 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-mhg6-2q2v-9h2c

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# Patch Next advisory brief: CVE-2026-31830

Advisory: sigstore-ruby verifier returns success for DSSE bundles with mismatched in-toto subject digest
IDs: CVE-2026-31830, GHSA-mhg6-2q2v-9h2c
Record: https://patchnext.com/advisories/cve-2026-31830 (revision 1, source checked 26 Oct 2026, 15:51 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: sigstore 0.2.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems sigstore: affected < 0.2.3; fixed in 0.2.3

## Suggested inspection (read-only)
- RubyGems sigstore: 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 sigstore.
- 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-mhg6-2q2v-9h2c (GitHub-reviewed advisory GHSA-mhg6-2q2v-9h2c lists affected ranges: RubyGems sigstore >=0 <0.2.3)

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