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GHSA-r78f-4q2q-hvv4
No affected components available
Summary
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.
Details
The revocation schema that is part of the Ursa CL-Signatures implementation 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.
The flaw exists in all CL-Signature versions published from the Hyperledger Ursa repository to the Ursa Rust Crate, and are fixed in all versions published from the Hyperledger AnonCreds CL-Signatures repository to the AnonCreds CL-Signatures Rust Crate.
To exploit the flaw, a holder must update their wallet (agent) software, replacing the Hyperledger Ursa or AnonCreds CL-Signatures library that generates the proof of non-revocation. This may involve, for example, altering an iOS or Android application published in the respective app stores. A mitigation for this flaw is to use the application attestation capabilities (such as the Android "SafetyNet Attestation API") offered by the app store vendors to (for example) "help determine whether your servers are interacting with your genuine app running on a genuine Android device."
The problem is created in the generation of a revocation registry, prior to issuing any credentials. As such, to eliminate the impact of the flaw, the issued credentials must be re-issued based on a correct revocation registry, generated from a correct implementation, such as Hyperledger AnonCreds CL-Signatures.
Impact
The potential impact is as follows:
- A verifier may verify a credential from a holder as being "not revoked" when in fact, the holder's credential has been revoked.
Mitigation
Upgrade libraries/applications using the Ursa Rust Crate to any version of the AnonCreds CL-Signatures Rust Crate. If your application has issued revocable credentials, once the Issuer library has been upgraded, new revocation registries must be created, and credentials issued from revocation registries created with the the flawed software must be revoked and reissued.
A verifier can detect if a holder presents a flawed revocable credential.
The vulnerability requires physical access to the device to be exploited. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker needs high-level or administrative privileges. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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