CVE-2026-31830 is a high-severity security vulnerability in sigstore (rubygems), affecting versions < 0.2.3. It is fixed in 0.2.3.
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 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.
CVE-2026-31830 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (0.2.3). Upgrading removes the vulnerable code path.
rubygems
sigstore (< 0.2.3)sigstore → 0.2.3 (rubygems)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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Already deployed Kodem? See CVE-2026-31830 in your environment →Upgrade sigstore to 0.2.3 or later to resolve this vulnerability.
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CVE-2026-31830 is a high-severity security vulnerability in sigstore (rubygems), affecting versions < 0.2.3. It is fixed in 0.2.3.
CVE-2026-31830 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
sigstore (rubygems) versions < 0.2.3 is affected.
Yes. CVE-2026-31830 is fixed in 0.2.3. Upgrade to this version or later.
Whether CVE-2026-31830 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade sigstore to 0.2.3 or later.