# HTTP request smuggling / desynchronization

Two HTTP-processing components disagree about request boundaries or parsing.

**Candidate CWE:** [CWE-444](https://cwe.mitre.org/data/definitions/444.html)

## Test hypothesis

Use an isolated front-end/backend pool. Capture normal paired traffic, introduce one lab framing discrepancy, and compare each layer’s parsed request count and boundaries with rejection controls.

## Evidence required

Logs or byte traces demonstrate the mismatch and a controlled security consequence. Distinguish HTTP/1 framing from HTTP/2 translation; all follow-up requests must be yours.

## Rule out false positives

A timeout, 400/502, unsupported Transfer-Encoding, or a tool-normalized malformed request alone does not demonstrate desynchronization.

## Playbook and command references

- [Proxy normalization, cache isolation, and request boundaries](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/modules/proxy-cache.html) — Investigate layered HTTP behavior with isolated cache keys and controlled front-end/back-end traffic.

[Find the associated command snippets](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/commands.html?q=Proxy%20normalization%2C%20cache%20isolation%2C%20and%20request%20boundaries)

## Referenced by these target playbooks

[Web & API](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/web-api.html) · [OSS & self-hosted](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/oss.html) · [Cloud & containers](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/cloud.html) · [Network services](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/network.html)

## Report checklist

- [ ] Capture the affected version, configuration, identities, and object ownership.
- [ ] Preserve a valid baseline and a negative control.
- [ ] Reproduce the forbidden data access, action, or state change on controlled fixtures.
- [ ] Explain the intended security rule and why the observed behavior violates it.
- [ ] State prerequisites, uncertainty, cleanup, and the smallest demonstrated impact.

## Conditional ATT&CK mapping

No direct ATT&CK mapping selected. Record the weakness and demonstrated impact without forcing an adversary-behavior classification. See the [mapping guide](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/attack.html).

## Primary references

- [PortSwigger request smuggling](https://portswigger.net/web-security/request-smuggling)

[Back to the complete vulnerability catalog](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/vulnerabilities.html)