{"id":"GHSA-mhg6-2q2v-9h2c","summary":"sigstore-ruby verifier returns success for DSSE bundles with mismatched in-toto subject digest","details":"### Summary\n\n`Sigstore::Verifier#verify` does not propagate the `VerificationFailure` returned by `verify_in_toto` 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.\n\n### Details\n\nIn `lib/sigstore/verifier.rb`, the verify method calls `verify_in_toto` (line 176) without capturing or checking its return value:\n\n`verify_in_toto(input, in_toto)`\n\nWhen `verify_in_toto` 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.\n\nThe message_signature code path is not affected.\n\n### Impact\n\nAn attacker who possesses a valid signed DSSE bundle containing an in-toto attestation for artifact A can present it as a valid attestation for a different artifact B. All other verification checks (DSSE envelope signature, certificate chain, Rekor inclusion, SCTs, policy) pass because they are independent of the artifact content. Only the in-toto subject digest check detects the mismatch, and its result is discarded.\n\nThis allows an attacker to bypass artifact-to-attestation binding for any consumer that relies on `Sigstore::Verifier#verify` to validate DSSE/in-toto bundles.\n\n### Workarounds\n\nNone. Consumers cannot work around this without patching the library.","aliases":["CVE-2026-31830"],"modified":"2026-03-19T21:17:24.743250Z","published":"2026-03-11T00:24:42Z","database_specific":{"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-03-11T00:24:42Z","nvd_published_at":"2026-03-10T22:16:21Z","cwe_ids":["CWE-252"]},"references":[{"type":"WEB","url":"https://github.com/sigstore/sigstore-ruby/security/advisories/GHSA-mhg6-2q2v-9h2c"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31830"},{"type":"WEB","url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/sigstore/CVE-2026-31830.yml"},{"type":"PACKAGE","url":"https://github.com/sigstore/sigstore-ruby"}],"affected":[{"package":{"name":"sigstore","ecosystem":"RubyGems","purl":"pkg:gem/sigstore"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.2.3"}]}],"versions":["0.1.1","0.2.0","0.2.1","0.2.2"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-mhg6-2q2v-9h2c/GHSA-mhg6-2q2v-9h2c.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"}]}