CVE-2024-7885 is a concurrency vulnerability classified as a race condition in the Undertow web server's ProxyProtocolReadListener component. The issue arises because the parseProxyProtocolV1 method reuses a single StringBuilder instance across multiple HTTP requests on the same persistent connection without proper synchronization. This shared mutable state can cause data from one request to be inadvertently read or written during the processing of another request, leading to unintended data leakage between requests or responses. The vulnerability primarily manifests as errors and premature connection termination, but more critically, it risks exposing sensitive data from previous requests to subsequent ones. The flaw affects Undertow versions from 0 up to 2.3.0.Alpha1 and does not require any authentication or user interaction to exploit. The CVSS 3.1 score of 7.5 reflects the network attack vector, low attack complexity, and no privileges required, with a high impact on availability but no direct impact on confidentiality or integrity according to the vector. However, the potential for data leakage indicates some confidentiality impact not fully captured in the vector. No known exploits are currently reported in the wild. The vulnerability is particularly relevant in environments where Undertow is used as a proxy or load balancer handling multiple requests over persistent connections, common in microservices and cloud-native deployments.

For European organizations, this vulnerability poses a dual threat: service disruption and potential data leakage. The improper synchronization can cause connection errors and premature termination, impacting availability of web services relying on Undertow, which may degrade user experience and business operations. More critically, the risk of data leakage between requests could expose sensitive information such as authentication tokens, personal data, or internal headers, violating data protection regulations like GDPR. Organizations operating multi-tenant platforms or handling sensitive customer data are at heightened risk. The vulnerability's ease of exploitation without authentication increases the attack surface, especially for public-facing services. Disruption or data leakage incidents could lead to reputational damage, regulatory fines, and operational costs. Given Undertow's usage in Java-based middleware and application servers, sectors such as finance, telecommunications, and government services in Europe could be particularly impacted.

Immediate mitigation involves upgrading Undertow to a version where this race condition is fixed; organizations should monitor official Undertow or Red Hat advisories for patches. Until patches are available, organizations should consider disabling Proxy Protocol support if feasible or isolating traffic to minimize multi-request reuse on the same connection. Implementing strict connection management policies, such as limiting persistent connections or enforcing request serialization, can reduce the risk. Application-level mitigations include sanitizing and validating all incoming proxy headers and monitoring logs for unusual connection errors or data anomalies. Network-level controls like Web Application Firewalls (WAFs) can help detect and block suspicious traffic patterns exploiting this flaw. Additionally, conducting thorough code reviews and testing for concurrency issues in custom middleware components can prevent similar vulnerabilities. Finally, organizations should ensure incident response plans include scenarios for data leakage and service disruption to minimize impact.