GHSA-MHG6-2Q2V-9H2C

Vulnerability from github – Published: 2026-03-11 00:24 – Updated: 2026-03-19 21:02
VLAI?
Summary
sigstore-ruby verifier returns success for DSSE bundles with mismatched in-toto subject digest
Details

Summary

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.

Details

In lib/sigstore/verifier.rb, the verify method calls verify_in_toto (line 176) without capturing or checking its return value:

verify_in_toto(input, in_toto)

When 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.

The message_signature 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 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.

This allows an attacker to bypass artifact-to-attestation binding for any consumer that relies on Sigstore::Verifier#verify to validate DSSE/in-toto bundles.

Workarounds

None. Consumers cannot work around this without patching the library.

Severity ?
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "RubyGems",
        "name": "sigstore"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.2.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-31830"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-252"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-11T00:24:42Z",
    "nvd_published_at": "2026-03-10T22:16:21Z",
    "severity": "HIGH"
  },
  "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.",
  "id": "GHSA-mhg6-2q2v-9h2c",
  "modified": "2026-03-19T21:02:46Z",
  "published": "2026-03-11T00:24:42Z",
  "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"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "sigstore-ruby verifier returns success for DSSE bundles with mismatched in-toto subject digest"
}


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