Web Cache Poisoning

Summary

Web Cache Poisoning is an application attack where an attacker manipulates the caching mechanism of a web server or proxy to serve malicious or altered content to users. By injecting crafted requests, the attacker causes the cache to store harmful responses, which are then delivered to subsequent users, potentially leading to data theft, session hijacking, or distribution of malware.

Key Characteristics

• Exploits vulnerabilities in web caching systems such as reverse proxies, CDNs, or browser caches.
• Targets cache key construction flaws, allowing attackers to poison cached content.
• Can affect both dynamic and static content, resulting in widespread impact.
• Often leverages HTTP header manipulation or URL parameter tampering.
• May result in persistent delivery of malicious content until cache expiration or purge.

Defensive Controls

• Implement strict cache key validation and normalization to prevent unauthorized variations.
• Use cache-control headers correctly to limit caching of sensitive or dynamic content.
• Sanitize and validate all user inputs, including headers and URL parameters.
• Regularly monitor and audit cache behavior for anomalies or unexpected content.
• Deploy web application firewalls (WAFs) with rules to detect and block cache poisoning attempts.

Related Security Solutions

Web Cache Poisoning defenses often involve web application firewalls (WAFs), secure content delivery networks (CDNs) with robust cache management, input validation frameworks, and security monitoring tools that detect anomalous cache behavior.