GHSA-2q6j-gqc4-4gw3
LOWBreaking unlinkability in Identity Mixer using malicious keys
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.
Blast Radius
anoncreds-clsignatures🦀ursaReal-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
CL Signatures Issuer Key Correctness Proof lacks of prime strength checking
A weakness in the Hyperledger AnonCreds specification that is not mitigated in the Ursa and AnonCreds implementations is that the Issuer does not publish a key correctness proof demonstrating that a generated private key is sufficient to meet the unlinkability guarantees of AnonCreds. A sufficient private key is one in which it's components p and q are safe primes, such that:
pandqare both prime numberspandqare not equalpandqhave the same, sufficiently large, size- For example, using two values both 1024 bits long is sufficient, whereas using one value 2040 bits long and the other 8 bits long is not.
The Ursa and AnonCreds CL-Signatures implementations always generate a sufficient private key. A malicious issuer could in theory create a custom CL Signature implementation (derived from the Ursa or AnonCreds CL-Signatures implementations) that uses weakened private keys such that presentations from holders could be shared by verifiers to the issuer who could determine the holder to which the credential was issued.
Impact
This vulnerability could impact holders of AnonCreds credentials implemented using the CL-signature scheme in the Ursa and AnonCreds implementations of CL Signatures.
Mitigations
Jan Camenisch and Markus Michels. Proving in zero-knowledge that a number is the product of two safe primes (pages 12-13) demonstrates a key correctness proof that could be used to show the issuer has generated a sufficiently strong private key, proving the characteristics listed above.
In a future version of AnonCreds, the additional key correctness proof could be published separately or added to the Credential Definition. In the meantime, Issuers in existing ecosystems can share such a proof with their ecosystem co-participants in an ad hoc manner.
The lack of such a published key correctness proof allows a malicious Issuer to deliberately generate a private key that lacks the requirements listed above, enabling the Issuer to perform a brute force attack on presentations provided to colluding verifiers that breaks the unlinkability guarantee of AnonCreds.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | anoncreds-clsignatures | all versions | No fix |
| 🦀crates.io | ursa | all versions | No fix |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for anoncreds-clsignatures. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of anoncreds-clsignatures has shipped for GHSA-2q6j-gqc4-4gw3 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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 pinpoints whether GHSA-2q6j-gqc4-4gw3 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-2q6j-gqc4-4gw3. 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-2q6j-gqc4-4gw3 in your dependencies?
O3 detects GHSA-2q6j-gqc4-4gw3 across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.