# CVE-2022-31021: Unlinkability broken in ursa when verifiers use malicious keys > A malicious issuer can break unlinkability in AnonCreds credentials by using weakened private keys, allowing them to track holders. - **Severity:** Low 3.3 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Local or same network only - **Victim action needed:** A user has to click or open something - **Fix available:** No - **Published:** 16 Jan 2024 - **Updated:** 2 Jun 2025 - **Also known as:** GHSA-2q6j-gqc4-4gw3 ## What is CVE-2022-31021? CVE-2022-31021 is a low-severity vulnerability in hyperledger ursa, published on 16 Jan 2024. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link. ### Official description Ursa is a cryptographic library for use with blockchains. 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. 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. This vulnerability could impact holders of AnonCreds credentials implemented using the CL-signature scheme in the Ursa and AnonCreds implementations of CL Signatures. The ursa project has has moved to end-of-life status and no fix is expected. Weakness: CWE-829 (Inclusion of Functionality from Untrusted Control Sphere) ## Which versions are affected by CVE-2022-31021? 4 open source packages ship an affected version, including ursa and anoncreds-clsignatures. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `ursa` | crates.io | All versions to 0.3.7 | None | | `ursa` | crates.io | All versions to 0.3.7 | None | | `anoncreds-clsignatures` | crates.io | All versions | None | | `anoncreds-clsignatures` | crates.io | All versions | None | Products: Hyperledger Ursa. ## How do I fix CVE-2022-31021? No fix has been published for CVE-2022-31021 yet. Limit exposure of the affected software until one is available. ## Is CVE-2022-31021 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2022-31021 exists. ## Other vulnerabilities in hyperledger ursa - [CVE-2024-21670](https://insights.sbomify.com/CVE-2024-21670/): CL-Signatures Revocation Scheme in Ursa has flaws that allow a holder to demonstrate non-revocation of a revoked credential (medium 6.5) - [CVE-2024-22192](https://insights.sbomify.com/CVE-2024-22192/): Ursa CL-Signatures Revocation allows verifiers to generate unique identifiers for holders (medium 6.5) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2022-31021 and fix it if it is affected. What it is: CVE-2022-31021 is a low-severity vulnerability in hyperledger ursa, published on 16 Jan 2024. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2022-31021 exists. Affected packages and fixed versions: - ursa (crates.io): affected all versions up to 0.3.7; no fix listed - ursa (crates.io): affected all versions up to 0.3.7; no fix listed - anoncreds-clsignatures (crates.io): affected all versions; no fix listed - anoncreds-clsignatures (crates.io): affected all versions; no fix listed Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2022-31021/ (Markdown: https://insights.sbomify.com/CVE-2022-31021/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2022-31021 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-31021 - OSV: https://osv.dev/vulnerability/CVE-2022-31021 --- From sbomify Insights: https://insights.sbomify.com/CVE-2022-31021/ Summaries are generated and may contain mistakes; the official description above is the record.