CVE-2025-66017 identifies a cryptographic vulnerability in the LFDT-Lockness cggmp21 (<= 0.6.3) and cggmp24 (0.7.0-alpha.1) libraries, which implement an advanced ECDSA Threshold Signature Scheme (TSS) protocol. This protocol supports efficient 1-round signing with preprocessing and includes features like identifiable abort and key refresh. However, in the affected versions, the handling of presignatures—precomputed signature components intended to optimize signing—can be misused in a manner that significantly weakens the cryptographic security guarantees. Specifically, the vulnerability stems from the use of a broken or risky cryptographic algorithm (CWE-327), which undermines the integrity of the signature process. The flaw allows an attacker to exploit presignatures to potentially forge signatures or compromise the threshold signing process without requiring authentication or user interaction, and can be exploited remotely over the network. The vulnerability has been addressed in cggmp24 version 0.7.0-alpha.2, which introduces API changes that prevent presignatures from being used insecurely. Despite the absence of known exploits in the wild, the high CVSS 8.7 score reflects the critical nature of the cryptographic weakness and the potential for severe impact if exploited.

For European organizations, especially those involved in financial services, government, telecommunications, and critical infrastructure, this vulnerability poses a significant risk. The compromised cryptographic integrity could lead to unauthorized signature forgeries, undermining trust in digital transactions, secure communications, and identity verification processes. This may result in data breaches, fraudulent transactions, and loss of regulatory compliance, particularly under GDPR and other data protection frameworks. Organizations using the affected cggmp21 or cggmp24 libraries in their security-critical applications could face operational disruptions and reputational damage. The remote and unauthenticated nature of the exploit increases the attack surface, making it easier for threat actors to target vulnerable systems across Europe. Given the strategic importance of secure cryptographic protocols in sectors like banking, government, and technology, the impact could be widespread if not promptly mitigated.

European organizations should immediately audit their software supply chains and internal applications to identify usage of the affected cggmp21 (<= 0.6.3) and cggmp24 (0.7.0-alpha.1) versions. The primary mitigation is to upgrade to cggmp24 version 0.7.0-alpha.2 or later, which contains API changes that eliminate insecure presignature usage. Where upgrading is not immediately feasible, organizations should implement strict controls to prevent the use of presignatures in vulnerable contexts, including code reviews and runtime monitoring for suspicious cryptographic operations. Additionally, organizations should enforce network-level protections such as segmentation and intrusion detection systems tuned to detect anomalous cryptographic traffic patterns. Cryptographic key management policies should be reviewed and strengthened to include key rotation and revocation procedures in case of compromise. Finally, organizations should monitor threat intelligence feeds for any emerging exploits related to this vulnerability and prepare incident response plans accordingly.