Identification of Web Cache Poisoning

Web cache poisoning is a type of attack where an attacker exploits vulnerabilities in web caching systems to cache malicious content or poison the cache with harmful data. This can lead to various security risks, such as delivering malicious content to users, bypassing security controls, or causing denial of service. Identifying web cache poisoning involves examining how the caching mechanisms are implemented and looking for vulnerabilities that could be exploited by an attacker. Here's how you can identify web cache poisoning vulnerabilities:


  1. Analysis of Caching Headers: Review HTTP responses from the server to check for caching headers such as Cache-Control, Expires, Last-Modified, and ETag. Look for inconsistencies or weaknesses in how caching directives are applied.
  2. Testing Cacheability of User-Generated Content: Check if user-generated content (e.g., comments, profile information) is being cached by the server or intermediary caches. This content should not be cached to prevent poisoning attacks.
  3. Investigation of Cache Key Generation: Examine how cache keys are generated to determine if they include user-controllable input or sensitive data. Improperly crafted cache keys can lead to cache poisoning.
  4. Manipulating Cache-Control Headers: Attempt to manipulate Cache-Control headers in requests to see if you can influence caching behavior. For example, try setting Cache-Control: public to force caching of sensitive or user-specific content.
  5. Analyzing Cache Invalidation: Review how the application handles cache invalidation requests. Look for weaknesses in cache purging mechanisms that could be exploited to poison the cache.
  6. Testing for Cache Busting: Attempt cache poisoning attacks by injecting cache-busting techniques such as random query parameters or request headers to bypass caching controls and manipulate cache content.


  • Example 1: During testing, a penetration tester discovers that the application caches responses to requests containing sensitive user information, such as account details or session tokens. By manipulating caching headers, the tester is able to poison the cache and retrieve sensitive data from subsequent requests.
  • Example 2: The tester finds that the application's cache key generation algorithm includes user-controlled input, such as request parameters or headers. By injecting malicious input into cache keys, the tester is able to poison the cache with malicious content.


  1. Avoid Caching Sensitive Data: Ensure that sensitive information, user-specific content, and dynamic data are not cached by the server or intermediary caches.
  2. Strict Cache Control Headers: Implement strict cache control headers to prevent caching of sensitive content and ensure proper cache validation and expiration.
  3. Secure Cache Key Generation: Generate cache keys using secure and deterministic methods that do not include user-controllable input or sensitive data.
  4. Regular Cache Auditing: Regularly audit and monitor cache behavior to detect and mitigate potential cache poisoning attacks.
  5. Security Headers: Implement security headers such as Cache-Control: no-store to prevent caching of sensitive information and reduce the risk of cache poisoning.
  6. Security Testing: Conduct regular security testing, including vulnerability scanning and manual testing, to identify and address cache poisoning vulnerabilities in web applications.

By identifying and mitigating web cache poisoning vulnerabilities, organizations can prevent the delivery of malicious content to users, protect sensitive information, and maintain the integrity of their web applications.