The vulnerability identified as CVE-2025-66031 affects the node-forge library, a widely used JavaScript implementation of Transport Layer Security (TLS) and cryptographic functions. The root cause is an uncontrolled recursion flaw (CWE-674) in the ASN.1 DER parsing logic. ASN.1 (Abstract Syntax Notation One) is a standard interface description language for defining data structures used in cryptography and network protocols. Node-forge versions 1.3.1 and earlier do not properly limit recursion depth when parsing ASN.1 structures, allowing attackers to craft deeply nested DER-encoded inputs. When such malicious inputs are processed, the recursive parsing leads to stack exhaustion, causing the application to crash or become unresponsive, resulting in a Denial-of-Service (DoS). The vulnerability can be exploited remotely without any authentication or user interaction, making it particularly dangerous for exposed services that parse untrusted ASN.1 data. The CVSS 4.0 base score of 8.7 reflects the high impact on availability and the ease of exploitation. The issue was publicly disclosed on November 26, 2025, and fixed in node-forge version 1.3.2. No public exploits have been reported yet, but the vulnerability poses a significant risk to any system using vulnerable versions of node-forge for TLS or cryptographic operations, especially in web applications and network services.

For European organizations, the primary impact of CVE-2025-66031 is the potential for Denial-of-Service attacks against services relying on node-forge for TLS or cryptographic processing. This can disrupt availability of critical applications, including secure communications, identity verification, and data encryption services. Organizations in sectors such as finance, healthcare, government, and telecommunications are particularly at risk due to their reliance on secure cryptographic libraries. The vulnerability could be exploited to degrade service performance or cause outages, impacting business continuity and potentially leading to regulatory compliance issues under GDPR if services become unavailable. Since the vulnerability does not compromise confidentiality or integrity directly, the main concern is service disruption. However, prolonged outages could indirectly affect data protection and trust. European organizations using node-forge in client-side or server-side JavaScript environments must assess their exposure and remediate promptly to avoid operational impacts.

European organizations should immediately audit their software dependencies to identify any usage of node-forge versions prior to 1.3.2. The primary mitigation is to upgrade all instances of node-forge to version 1.3.2 or later, where the uncontrolled recursion flaw has been patched. For environments where immediate upgrade is not feasible, implementing input validation and limiting the depth of ASN.1 structures before parsing can reduce risk. Network-level protections such as Web Application Firewalls (WAFs) can be tuned to detect and block suspiciously deep or malformed ASN.1 DER inputs. Additionally, monitoring application logs for stack overflow or crash patterns related to ASN.1 parsing can help detect exploitation attempts. Organizations should also review their incident response plans to handle potential DoS attacks targeting this vulnerability. Finally, developers should adopt secure coding practices to avoid similar recursive parsing issues in the future and consider fuzz testing ASN.1 parsers to identify vulnerabilities proactively.