CVE-2021-41119 is a vulnerability classified under CWE-400 (Uncontrolled Resource Consumption) affecting the wire-server component of the Wire application backend services. Wire-server acts as the system server managing backend operations for Wire's communication platform. Versions prior to 2022-03-01 are vulnerable to a denial of service (DoS) attack that exploits a crafted object designed to cause a hash collision during parsing. This hash collision triggers a worst-case quadratic time complexity in the server's parsing logic, significantly increasing CPU and memory consumption. Under heavy load or targeted attack, this resource exhaustion can degrade server performance or cause complete service unavailability. The vulnerability does not require authentication or user interaction, making it exploitable remotely by sending maliciously crafted requests to the wire-server. The issue has been resolved in version 2022-03-01, which is already deployed on all Wire-managed services. However, on-premise deployments running earlier versions remain at risk. No known workarounds exist, so updating to the fixed version is the only effective mitigation. There are no known exploits in the wild reported to date, but the vulnerability's nature means it could be leveraged for DoS attacks against organizations relying on vulnerable wire-server instances.

For European organizations using Wire's on-premise wire-server versions prior to 2022-03-01, this vulnerability poses a significant risk of denial of service. The attack can cause service outages, disrupting internal and external communications, potentially affecting business continuity and operational efficiency. Organizations in sectors with high communication demands—such as finance, healthcare, and government—may experience amplified impact due to reliance on real-time messaging and collaboration. Additionally, prolonged outages could lead to reputational damage and compliance issues, especially where communication availability is regulated. Since the vulnerability can be exploited remotely without authentication, attackers could launch DoS attacks from outside the network, increasing the threat surface. Although no data confidentiality or integrity issues are directly associated, the availability impact alone can have cascading effects on dependent systems and services. The lack of workarounds means organizations must prioritize patching to prevent exploitation.

1. Immediate upgrade of all on-premise wire-server instances to version 2022-03-01 or later to eliminate the vulnerability. 2. Implement network-level protections such as rate limiting and anomaly detection on incoming traffic to wire-server endpoints to identify and block suspicious request patterns that may indicate hash collision attacks. 3. Deploy Web Application Firewalls (WAFs) with custom rules targeting known malicious payload characteristics related to hash collision attempts. 4. Monitor server performance metrics closely for unusual spikes in CPU or memory usage that could signal exploitation attempts. 5. Conduct regular security audits and penetration testing focusing on resource exhaustion vectors to proactively identify similar weaknesses. 6. Isolate wire-server instances behind segmented network zones with strict access controls to limit exposure. 7. Maintain up-to-date incident response plans that include procedures for DoS attack mitigation and recovery specific to wire-server services. These steps go beyond generic patching advice by emphasizing proactive detection, network controls, and operational readiness.