CVE-2022-31021 — anoncreds-clsignatures
LOWCVE-2022-31021 is a low-severity (CVSS 3.3) CWE-829 vulnerability in anoncreds-clsignatures. 1 public exploit reference exists, so weaponization risk is real. No vendor fix is recorded yet; mitigation options are listed below.
Unlinkability broken in ursa when verifiers use malicious keys
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2022-31021.
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
CVE-2022-31021 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 378,567 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
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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of anoncreds-clsignatures has shipped for CVE-2022-31021 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2022-31021 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2022-31021. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2022-31021 in your dependencies?
O3 Security finds CVE-2022-31021 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.