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NoorQureshiNoorQureshi/ronin/skills/web/web-cache-deception/SKILL.md

web-cache-deception

Skill26 starsChanged 32 days agoMITView on GitHub

Trick a CDN/cache into storing a victim's authenticated response at a public URL, then read it. Load on "web cache deception", when a CDN/cache sits in front of an app that serves per-user content, or to test whether private pages can be cached. Signals: `X-Cache`/`CF-Cache-Status` headers, caching by file extension, static-looking suffixes on dynamic endpoints.

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SKILL.md

Web cache deception

When it applies

A caching layer (CDN, reverse proxy) fronts an app that returns per-user content, and the cache decides what to store by URL pattern/extension. If you can make an authenticated response look cacheable, the cache stores it — and anyone can then fetch that victim's data.

Why it works

The cache and the origin disagree about the URL. The cache sees /account.css and thinks "static, cache it"; the origin ignores the .css suffix (or a delimiter) and serves the dynamic /account page. The victim's private response gets stored under a public key you can request.

Method

  1. Confirm the mismatch: request an authenticated page with a static suffix — /account/foo.css, /account%0a.css, /account;foo.js, /account%2ffoo.css. If the origin still returns the account page (not 404), the origin is ignoring the suffix.
  2. Confirm caching: repeat and watch X-Cache/CF-Cache-Status flip to HIT, or a Age header appear. A cached, authenticated response is the vulnerability.
  3. Prove cross-user impact: as the victim, visit the crafted URL once (or have them); then as an unauthenticated attacker request the same URL and receive the victim's private data.
  4. Explore delimiters/normalisation: caches and origins normalise ;, %2f, //, .., trailing dots differently — Param Miner's rules or manual fuzzing find the pair that splits them.
  5. Report with least data: prove one private field leaked; don't hoard victim data.

Gotchas

  • This is not cache poisoning: deception caches a victim's real response; poisoning injects a malicious response via unkeyed input. Different bug, different report (web-cache-poisoning).
  • Needs a genuinely cacheable-looking key and an origin that ignores it — confirm both.
  • Some CDNs cache by content-type, not extension — test path-based tricks too.

Verify success

An unauthenticated request retrieves another user's authenticated content from the cache (HIT/Age present), reproducibly.

References

Omer Gil "Web Cache Deception"; PortSwigger web cache deception labs; CDN caching-rule docs.

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