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Fencer Vulns
medium 6.5

CVE-2024-21670 json

CL-Signatures Revocation Scheme in Ursa has flaws that allow a holder to demonstrate non-revocation of a revoked credential

published 2024-01-16 2 y ago modified 2026-09-10 1 mo ago also GHSA-r78f-4q2q-hvv4 , EUVD-2024-0413

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 20%
public exploits
0
none known

Summary

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 A verifier may verify a credential from a holder as being "not revoked" when in fact, the holder's credential has been revoked.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.

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
2 y ago

Exploit prediction

0.28% chance of exploitation in the next 30 days, higher than 20% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:P/AC:H/PR:H/UI:R/S:C/C:H/I:H/A:N
NVD 3.1 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
GitHub 3.1 6.5 CVSS:3.1/AV:P/AC:H/PR:H/UI:R/S:C/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
crates.io ursa
<=0.3.7
 no fix listed
crates.io anoncreds-clsignatures
all versions
 no fix listed

Affected products

  • hyperledger-archives ursa
  • hyperledger ursa

Classification

Weakness
  • CWE-327 Use of a Broken or Risky Cryptographic Algorithm

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.