CVE-2024-22192 in ursa
Summary
by MITRE • 01/17/2024
Ursa is a cryptographic library for use with blockchains. The revocation scheme 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. Notably, a malicious verifier may be able to generate a unique identifier for a holder providing a verifiable presentation that includes a Non-Revocation proof. The impact of the flaw is that a malicious verifier may be able to determine a unique identifier for a holder presenting a Non-Revocation proof. Ursa has moved to end-of-life status and no fix is expected.
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Analysis
by VulDB Data Team • 01/17/2024
The vulnerability identified as CVE-2024-22192 resides within the Ursa cryptographic library, a component specifically designed for blockchain applications and supporting the CL-Signatures implementation. This library serves as a critical foundation for anonymous credential systems, particularly those implementing the AnonCreds verifiable credential model that is widely adopted in decentralized identity solutions. The flaw manifests in the revocation scheme that is integral to the CL-Signatures protocol, which is designed to maintain privacy while enabling the verification of credential validity. The issue directly undermines the privacy guarantees that the AnonCreds model is intended to provide, creating a significant security concern for systems relying on this cryptographic framework. The vulnerability operates at the intersection of cryptographic protocol design and privacy preservation, where the expected privacy protections are compromised due to implementation flaws in the revocation mechanism.
The technical flaw involves a weakness in how the Non-Revocation proof is constructed and validated within the Ursa library's implementation. When a holder presents a verifiable credential that includes a Non-Revocation proof, the malicious verifier can exploit the implementation gap to generate a unique identifier that can be used to track or correlate the holder across different presentation instances. This occurs because the revocation scheme does not properly prevent the extraction of identifying information from the cryptographic proofs, effectively breaking the unlinkability property that is fundamental to anonymous credential systems. The vulnerability stems from the improper handling of cryptographic commitments and zero-knowledge proof structures, where the mathematical properties that should ensure privacy are not adequately enforced. This flaw represents a direct violation of the expected cryptographic security model where the Non-Revocation proof should provide verification of credential validity without leaking holder-specific information, according to the established standards for anonymous credentials.
The operational impact of this vulnerability extends beyond simple privacy concerns to potentially enable sophisticated tracking and correlation attacks against users of systems implementing the AnonCreds model. Malicious verifiers can leverage this weakness to create persistent identifiers that link multiple credential presentations to the same holder, effectively destroying the privacy guarantees that the entire AnonCreds framework is built upon. This tracking capability could be exploited by adversaries to build detailed profiles of user behavior, establish connections between different online identities, or even perform surveillance activities that undermine the core purpose of anonymous credential systems. The implications are particularly severe for privacy-sensitive applications such as decentralized identity systems, privacy-preserving authentication mechanisms, and credential-based access control systems that depend on the unlinkability properties of anonymous credentials. The vulnerability affects any system that relies on Ursa's CL-Signatures implementation for revocation handling, potentially compromising the privacy of thousands of users across multiple applications and services.
The remediation approach for this vulnerability is severely limited due to the end-of-life status of the Ursa library, which means no official patches or updates are expected to be developed. Organizations relying on this library must consider immediate migration to alternative cryptographic implementations that properly support the AnonCreds model and provide robust privacy guarantees. The recommended mitigation strategy involves transitioning to well-maintained cryptographic libraries that have undergone proper security auditing and provide verified implementations of anonymous credential systems. Security teams should conduct comprehensive audits of their systems to identify all dependencies on Ursa and develop migration plans to more secure alternatives. This vulnerability highlights the critical importance of maintaining active support for cryptographic libraries and the risks associated with relying on end-of-life software components, particularly in privacy-sensitive applications where the consequences of security flaws can be severe and long-lasting.
This vulnerability aligns with CWE-310 (Cryptographic Issues) and CWE-327 (Use of a Broken or Risky Cryptographic Algorithm) categories, as it involves fundamental flaws in the cryptographic implementation that compromise security properties. From an ATT&CK framework perspective, this represents a privacy violation and information disclosure threat that could be categorized under T1566 (Phishing) and T1531 (Account Access Removal) when considering the potential for identity tracking and credential misuse. The flaw also demonstrates the broader risk of supply chain vulnerabilities in cryptographic libraries where a single implementation defect can compromise entire ecosystems of applications relying on that component for security. The vulnerability underscores the critical need for proper lifecycle management of cryptographic libraries and the importance of maintaining active security support for foundational cryptographic components in decentralized identity systems.