CVE-2025-4690 is a vulnerability identified in Google AngularJS, specifically in the 'linky' filter of the ngSanitize module. The linky filter is designed to detect URLs within input text using a regular expression. However, this regular expression suffers from inefficient complexity due to excessive backtracking, leading to a super-linear runtime when processing specially crafted inputs. This inefficiency can be exploited to perform a Regular Expression Denial of Service (ReDoS) attack, where an attacker submits input that causes the regex engine to consume excessive CPU resources, effectively degrading or denying service to legitimate users. The vulnerability affects all versions of AngularJS, which is notable because AngularJS has reached its End-of-Life (EOL) status and will no longer receive security updates or patches from the maintainers. The CVSS 3.1 base score is 4.3 (medium severity), reflecting that the attack can be launched remotely without privileges but requires user interaction (input submission). The impact is limited to availability degradation, with no direct confidentiality or integrity compromise. No known exploits are currently reported in the wild, and no patches are available due to the project's EOL status. This vulnerability is categorized under CWE-1333, which relates to inefficient regular expression complexity leading to performance issues.

For European organizations, the primary impact of CVE-2025-4690 is the potential for service disruption through ReDoS attacks targeting web applications that use AngularJS's linky filter. Organizations relying on legacy AngularJS applications, particularly those that process user-generated content with URL detection features, may experience degraded application responsiveness or downtime. This can affect customer-facing services, internal tools, or APIs, leading to operational disruptions and potential reputational damage. Since AngularJS is no longer maintained, organizations cannot rely on official patches, increasing the risk if mitigation is not implemented. The vulnerability does not directly expose sensitive data or allow unauthorized access, but availability impacts can indirectly affect business continuity and user trust. European sectors with high reliance on web applications, such as finance, e-commerce, public services, and telecommunications, could be particularly affected if AngularJS is in use. Additionally, compliance requirements under regulations like GDPR emphasize availability and service reliability, so disruptions could have regulatory implications.

Given the lack of official patches due to AngularJS's EOL status, European organizations should adopt a multi-layered mitigation approach: 1) Identify and inventory all applications using AngularJS, especially those utilizing the ngSanitize linky filter. 2) Where feasible, refactor or upgrade applications to use supported frameworks such as Angular (2+) or other modern alternatives that do not suffer from this vulnerability. 3) Implement input validation and sanitization at the server side to limit the size and complexity of user inputs, particularly those that trigger URL detection. 4) Employ Web Application Firewalls (WAFs) with custom rules to detect and block suspicious payloads that may exploit the regex inefficiency. 5) Monitor application performance metrics and logs to detect abnormal CPU usage patterns indicative of ReDoS attempts. 6) Consider rate limiting and CAPTCHA challenges on input forms to reduce automated attack attempts. 7) For legacy systems that cannot be immediately upgraded, isolate them in segmented network zones and restrict exposure to untrusted users. These targeted mitigations go beyond generic advice by focusing on compensating controls and proactive detection tailored to this specific regex-based DoS vector.