CVE-2022-41881 is a vulnerability in the Netty project, an event-driven asynchronous network application framework widely used for building high-performance network servers and clients. The vulnerability, classified under CWE-674 (Uncontrolled Recursion), affects Netty versions prior to 4.1.86.Final. Specifically, the issue arises when Netty parses a malformed or specially crafted message, which triggers an infinite recursion in the message decoding logic. This uncontrolled recursion leads to a StackOverflowError, causing the affected application to crash or become unresponsive. The root cause is a lack of proper input validation or recursion control in the message parsing code, which fails to handle malformed inputs gracefully. The vulnerability does not require authentication or user interaction to be exploited, as it can be triggered by sending a crafted network message to a vulnerable Netty-based service. There is no known workaround other than upgrading to version 4.1.86.Final or later, where the issue has been patched. Alternatively, a custom HaProxyMessageDecoder can be implemented to mitigate the risk. No known exploits have been reported in the wild, but the vulnerability poses a risk of denial-of-service (DoS) attacks by crashing network services that rely on vulnerable Netty versions.

For European organizations, the primary impact of CVE-2022-41881 is the potential for denial-of-service conditions in critical network infrastructure and applications that utilize vulnerable Netty versions. This can disrupt business operations, degrade service availability, and impact customer trust. Organizations in sectors such as finance, telecommunications, healthcare, and government, which often rely on high-availability network services, may experience service outages or degraded performance. The vulnerability affects the integrity and availability of services by causing unexpected crashes, but it does not directly compromise confidentiality or allow unauthorized access. However, service disruptions can indirectly affect operational integrity and availability. Given the widespread use of Netty in Java-based network applications, the scope of affected systems is broad, including web servers, proxies, microservices, and IoT gateways. The ease of exploitation is moderate since an attacker needs to send a crafted malformed message, which does not require authentication or user interaction, making remote exploitation feasible. The absence of known exploits in the wild suggests limited active targeting but does not eliminate the risk, especially as threat actors may develop exploits over time.

European organizations should prioritize upgrading all Netty dependencies to version 4.1.86.Final or later to eliminate the vulnerability. For environments where immediate upgrading is not feasible, implementing a custom HaProxyMessageDecoder can serve as a temporary mitigation to filter or sanitize incoming messages and prevent malformed inputs from triggering the recursion. Network-level protections such as intrusion detection and prevention systems (IDS/IPS) should be configured to detect and block anomalous or malformed traffic patterns targeting Netty-based services. Additionally, organizations should conduct thorough inventory and dependency analysis to identify all applications and services using vulnerable Netty versions. Continuous monitoring for unusual service crashes or StackOverflowError logs can help detect exploitation attempts. Security teams should also engage with software vendors and development teams to ensure timely patching and secure coding practices are followed to prevent similar issues. Finally, implementing rate limiting and network segmentation can reduce the attack surface and limit the impact of potential DoS attempts.