Suricata is a widely used open-source network Intrusion Detection System (IDS), Intrusion Prevention System (IPS), and Network Security Monitoring (NSM) engine. It uses Perl Compatible Regular Expressions (PCRE) for pattern matching in network traffic inspection. CVE-2025-29918 is a vulnerability classified under CWE-835 (Loop with Unreachable Exit Condition) that arises when a PCRE rule with a negated pattern is crafted in a way that causes Suricata's packet processing thread to enter an infinite loop. This infinite loop effectively halts the processing of network packets on the affected thread, leading to a denial of service condition. The vulnerability affects Suricata versions prior to 7.0.9 and was publicly disclosed in April 2025. The CVSS v3.1 score is 6.2 (medium severity), reflecting that the attack vector is local (AV:L), requires low attack complexity (AC:L), no privileges (PR:N), no user interaction (UI:N), and impacts availability only (A:H) without affecting confidentiality or integrity. This means an attacker capable of injecting or modifying PCRE rules can cause Suricata to become unresponsive in inline mode, reducing network visibility and potentially allowing malicious traffic to pass undetected. No known exploits are currently observed in the wild. The issue is resolved in Suricata 7.0.9, which should be applied to mitigate the risk. Organizations using Suricata in inline mode for real-time traffic inspection are particularly vulnerable to operational disruption if unpatched. The vulnerability underscores the importance of careful PCRE rule management and timely patching in network security tools.

For European organizations, this vulnerability primarily threatens the availability of Suricata-based network security monitoring and intrusion prevention systems. In environments where Suricata operates inline to block or inspect traffic, an infinite loop in packet processing can cause the system to become unresponsive, leading to a denial of service. This can result in reduced network visibility, delayed detection of malicious activity, and potential exposure to attacks that would otherwise be blocked or logged. Critical sectors such as finance, energy, telecommunications, and government agencies that rely on Suricata for real-time threat detection may experience operational disruptions or increased risk of undetected intrusions. The impact is particularly severe in high-throughput networks where continuous monitoring is essential. Although confidentiality and integrity are not directly compromised, the loss of availability can indirectly facilitate further attacks by creating blind spots. The absence of known exploits in the wild reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits targeting this vulnerability. European organizations must prioritize patching to maintain robust network defense capabilities.

1. Upgrade Suricata installations to version 7.0.9 or later immediately to apply the fix for CVE-2025-29918. 2. Audit existing PCRE rules for the use of negated patterns that could potentially trigger infinite loops; avoid or rewrite such rules where possible. 3. Implement strict controls and validation on who can create or modify PCRE rules to prevent malicious or accidental introduction of problematic patterns. 4. Monitor Suricata process health and thread responsiveness to detect signs of infinite loops or hangs early, enabling rapid response. 5. In environments where inline mode is critical, consider deploying redundant Suricata instances or failover mechanisms to maintain network visibility during outages. 6. Incorporate Suricata version and rule integrity checks into regular security audits and patch management processes. 7. Educate network security teams about the risks associated with complex PCRE rules and the importance of testing rules in staging environments before production deployment.