CVE-2025-5891 is a vulnerability identified in the Unitech pm2 process manager, specifically affecting versions 6.0.0 through 6.0.6. The issue resides in the /lib/tools/Config.js file, where inefficient regular expression complexity can be triggered by crafted input. This leads to a potential Denial of Service (DoS) condition due to excessive CPU consumption when the vulnerable regex is processed. The vulnerability can be exploited remotely without requiring user interaction or elevated privileges, making it accessible to unauthenticated attackers over the network. The CVSS 4.0 base score of 5.3 reflects a medium severity, indicating a moderate impact primarily on availability. The attack vector is network-based with low attack complexity and no privileges or user interaction needed. Although no known exploits are currently observed in the wild, the public disclosure of the vulnerability increases the risk of exploitation attempts. The vulnerability does not affect confidentiality or integrity directly but can degrade service availability by causing resource exhaustion. The lack of a patch link suggests that a fix may not yet be available or publicly released, emphasizing the need for mitigation strategies. Given pm2's role as a widely used Node.js process manager in production environments, this vulnerability could disrupt critical application uptime if exploited.

For European organizations, the impact of CVE-2025-5891 could be significant in environments relying on pm2 for managing Node.js applications, especially in sectors where high availability is critical such as finance, healthcare, and telecommunications. A successful exploitation could lead to service interruptions, affecting business continuity and potentially causing financial losses or reputational damage. Since the vulnerability allows remote exploitation without authentication, attackers could target exposed pm2 instances on public-facing infrastructure or within corporate networks. This could also facilitate lateral movement or be combined with other attacks to escalate impact. The medium severity rating suggests that while the threat is not critical, it should not be ignored, particularly in high-dependency scenarios. European organizations with stringent uptime requirements and regulatory obligations around service availability (e.g., GDPR mandates on data availability and integrity) may face compliance risks if disruptions occur. Additionally, the public disclosure raises the likelihood of automated scanning and exploitation attempts, increasing the urgency for mitigation.

1. Immediate mitigation should include restricting network exposure of pm2 management interfaces by implementing strict firewall rules and network segmentation to limit access only to trusted administrators or internal systems. 2. Monitor and audit pm2 logs and system resource usage for unusual spikes indicative of regex-based DoS attempts. 3. If possible, upgrade pm2 to a version beyond 6.0.6 once a patch is released by Unitech addressing this vulnerability. 4. In the absence of an official patch, consider applying temporary workarounds such as disabling or restricting features that process untrusted input through the vulnerable regex in /lib/tools/Config.js. 5. Employ Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) with custom rules to detect and block suspicious payloads targeting regex processing. 6. Conduct internal vulnerability scanning and penetration testing focused on pm2 instances to identify exposure and validate mitigation effectiveness. 7. Educate DevOps and security teams about this vulnerability to ensure rapid response and incident handling if exploitation attempts are detected.