CVE-2024-35296 is a vulnerability classified under CWE-20 (Improper Input Validation) affecting Apache Traffic Server, an open-source caching proxy server widely used to improve web performance and scalability. The flaw arises from the server's improper handling of the Accept-Encoding HTTP header, which is used by clients to specify supported content encodings such as gzip or deflate. When an invalid or malformed Accept-Encoding header is received, Apache Traffic Server fails to perform a cache lookup correctly. Instead of serving cached content, it forwards the request to the origin server, bypassing the cache layer. This behavior can lead to increased load on origin servers, reduced cache efficiency, and potential service degradation. The vulnerability affects all versions from 8.0.0 through 8.1.10 and 9.0.0 through 9.2.4. The issue does not expose confidential data directly but impacts the integrity of caching logic and availability due to resource strain. Exploitation requires no privileges or user interaction and can be triggered remotely by sending crafted HTTP requests with invalid Accept-Encoding headers. The Apache Software Foundation has addressed this issue in versions 8.1.11 and 9.2.5, recommending immediate upgrades to mitigate risk. No known active exploits have been reported, but the high CVSS score of 8.2 reflects the potential impact and ease of exploitation.

For European organizations, this vulnerability can lead to degraded web service performance and increased backend server load, potentially causing slower response times or partial service outages. Organizations relying on Apache Traffic Server for caching in high-traffic environments, such as e-commerce platforms, financial services, or public sector portals, may experience reduced availability and increased operational costs due to higher origin server resource consumption. While confidentiality is not directly impacted, the integrity of cache operations is compromised, which could affect content delivery consistency. The increased load might also expose systems to secondary risks, such as denial-of-service conditions if exploited at scale. Given the widespread use of Apache Traffic Server in content delivery networks and enterprise environments across Europe, the threat is significant, especially for critical infrastructure and services requiring high availability and performance.

European organizations should prioritize upgrading Apache Traffic Server to versions 8.1.11 or 9.2.5 immediately to remediate this vulnerability. In addition to patching, organizations should implement strict input validation and HTTP header sanitization at the network edge or via web application firewalls to detect and block malformed Accept-Encoding headers. Monitoring cache hit/miss ratios and backend server load can help identify anomalous traffic patterns indicative of exploitation attempts. Rate limiting requests with suspicious headers and deploying anomaly detection systems can further reduce risk. Organizations should also review and update incident response plans to include scenarios involving caching infrastructure degradation. Regular vulnerability scanning and penetration testing focused on HTTP header manipulation will help ensure ongoing resilience against similar input validation flaws.