GHSA-6698-mhxx-r84g is a medium-severity (CVSS 6.5) Broken Cryptographic Algorithm vulnerability in ursa. A fix is available for ursa — see the affected versions and patch details below.
Ursa CL-Signatures Revocation allows verifiers to generate unique identifiers for holders
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-6698-mhxx-r84g.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-6698-mhxx-r84g plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 376,715 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
ursa🦀anoncreds-clsignaturesReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The revocation scheme 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. Notably, a malicious verifier may be able to generate a unique identifier for a holder providing a verifiable presentation that includes a Non-Revocation proof.
Details
The revocation scheme 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, potentially allowing a malicious verifier to generate a unique identifier for a holder that provides a verifiable presentation that includes a Non-Revocation proof.
The flaws affects all CL-Signature versions published from the Hyperledger Ursa repository to the Ursa Rust Crate, and is fixed in all versions published from the Hyperledger AnonCreds CL-Signatures repository to the AnonCreds CL-Signatures Rust Crate.
The addressing the flaw requires updating AnonCreds holder software (such as mobile wallets) to a corrected CL-Signature implementation, such as the [AnonCreds CL Signatures Rust Crate]. Verifying presentations from corrected holders requires a updating the verifier software to a corrected CL-Signatures implementation. An updated verifier based on AnonCreds CL-Signatures can verify presentations from holders built on either the flawed Ursa CL-Signature implementation or a corrected CL-Signature implementation
The flaw occurs as a result of generating a verifiable presentation that includes a Non-Revocation proof from a flawed implementation.
Impact
The impact of the flaw is that a malicious verifier may be able to determine a unique identifier for a holder presenting a Non-Revocation proof.
Mitigation
Upgrade libraries/holder applications that generate AnonCreds verifiable presentations using the Ursa Rust Crate to any version of the AnonCreds CL-Signatures Rust Crate.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | ursa | all versions | No fix |
| 🦀crates.io | anoncreds-clsignatures | all versions | 0.1.0cargo update -p anoncreds-clsignatures --precise 0.1.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ursa, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
No patched version of ursa has shipped for GHSA-6698-mhxx-r84g yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-6698-mhxx-r84g can be triaged on real exposure rather than presence alone.
Tailored to GHSA-6698-mhxx-r84g. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-6698-mhxx-r84g in your dependencies?
O3 Security finds GHSA-6698-mhxx-r84g across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.