CVE-2025-12207 is a vulnerability identified in Kamailio version 5.5, specifically within the Grammar Rule Handler component's yyerror_at function located in src/core/cfg.y. The issue is a NULL pointer dereference caused by improper handling of configuration file inputs, which can lead to a crash of the Kamailio process. The vulnerability requires local access to the system and the ability to manipulate Kamailio configuration files, which limits the attack surface significantly. No authentication bypass or remote exploitation vector is present, and no user interaction is needed. The vulnerability has been publicly disclosed, and a proof-of-concept exploit is available, but practical exploitation scenarios are constrained by the need for local file manipulation. The vendor has not issued any patches or responded to the disclosure, leaving affected systems potentially vulnerable. The CVSS 4.0 score of 4.8 reflects a medium severity, primarily due to the limited attack vector (local access) and the impact being denial of service rather than code execution or data leakage. Kamailio is widely used in SIP-based VoIP infrastructures, so this vulnerability could disrupt telephony services if exploited.

For European organizations, the primary impact of CVE-2025-12207 is potential denial of service on Kamailio-based SIP servers, which could disrupt VoIP communications and related telephony services. This can affect enterprises, telecom providers, and service operators relying on Kamailio for session management. While the vulnerability does not directly compromise confidentiality or integrity, service unavailability can lead to operational disruptions and customer dissatisfaction. Organizations with multi-tenant or critical communications infrastructure may face increased risk if local access controls are weak, allowing attackers or malicious insiders to trigger the crash. The lack of vendor response and patch availability increases exposure duration. Given Kamailio's role in telecom infrastructure, disruption could have cascading effects on emergency services, call centers, and business communications within Europe.

Mitigation should focus on restricting local access to systems running Kamailio 5.5 to trusted administrators only, enforcing strict file system permissions on configuration files to prevent unauthorized modifications. Organizations should monitor Kamailio logs for unusual configuration changes or crashes indicative of exploitation attempts. Employing host-based intrusion detection systems (HIDS) can help detect local tampering. Until an official patch is released, consider upgrading to a later Kamailio version if available or applying community-developed patches if trustworthy. Additionally, implementing redundancy and failover mechanisms for SIP services can minimize impact from potential service disruptions. Regular backups of configuration files and system snapshots will aid in rapid recovery. Finally, engaging with the Kamailio community for updates or unofficial fixes is advisable given the vendor's lack of response.