fkie_cve-2024-21670

Ursa is a cryptographic library for use with blockchains. The revocation schema that is part of the Ursa CL-Signatures implementations has a flaw that could impact the privacy guarantees defined by the AnonCreds verifiable credential model, allowing a malicious holder of a revoked credential to generate a valid Non-Revocation Proof for that credential as part of an AnonCreds presentation. A verifier may verify a credential from a holder as being "not revoked" when in fact, the holder's credential has been revoked. Ursa has moved to end-of-life status and no fix is expected.

GHSA-r78f-4q2q-hvv4 — CL-Signatures Revocation Scheme in Ursa has flaws that allow a holder to demonstrate non-revocation of a revoked creden…

Affected: crates.io: ursa, crates.io: anoncreds-clsignatures

### Summary

The revocation schema that is part of the Ursa CL-Signatures implementations has a flaw that could impact the privacy guarantees defined by the AnonCreds verifiable credential model, allowing a malicious holder of a revoked credential to generate a valid Non-Revocation Proof for that credential as part of an AnonCreds presentation.

### Details

The revocation schema that is part of the Ursa CL-Signatures implementation has a flaw that could impact the privacy guarantees defined by the AnonCreds verifiable credential model, allowing a malicious holder of a revoked credential to generate a valid Non-Revocation Proof for that credential as part of an AnonCreds presentation.

The flaw exists in all CL-Signature versions published from the [Hyperledger Ursa] repository to the [Ursa Rust Crate], and are fixed in all versions published from the [Hyperledger AnonCreds CL-Signatures] repository to the [AnonCreds CL-Signatures Rust Crate].

To exploit the flaw, a holder must update their wallet (agent) software, replacing the Hyperledger Ursa or AnonCreds CL-Signatures library that generates the proof of non-revocation. This may involve, for example, altering an iOS or Android application published in the respective app stores. A mitigation for this flaw is to use the application attestation capabilities (such as the Android "[SafetyNet Attestation API]") offered by the app store vendors to (for example) "help determine whether your servers are interacting with your genu…

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EUVD-2026-3856

fkie_cve-2024-21670

GHSA-r78f-4q2q-hvv4 — CL-Signatures Revocation Scheme in Ursa has flaws that allow a holder to demonstrate non-revocation of a revoked creden…

gsd-2024-21670