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

> Remote attackers can desynchronize HTTP message boundaries in Rouille's proxy implementation, potentially bypassing security controls or modifying data.

- **Severity:** Medium 6.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Jul 2026
- **Updated:** 28 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-67181, GHSA-fgf8-ph7p-m275

## What is CVE-2026-67181?

CVE-2026-67181 is a medium-severity vulnerability in tomaka rouille, published on 28 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-444 (Inconsistent Interpretation of HTTP Requests)

## Which versions are affected by CVE-2026-67181?


## How do I fix CVE-2026-67181?

Upgrade to a fixed version.

## Is CVE-2026-67181 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-67181 exists.

Public exploit code:

-  Security Advisory: HTTP Request Smuggling via Transfer-Encoding Desynchronization (rouille) (github_poc): https://github.com/theopaid/CVE-2026-67181-HTTP-Request-Smuggling-via-Transfer-Encoding-Desynchronization-rouille-

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-67181 and fix it if it is affected.

What it is: CVE-2026-67181 is a medium-severity vulnerability in tomaka rouille, published on 28 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-67181 exists.

Affected product: tomaka rouille. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-67181/ (Markdown: https://insights.sbomify.com/CVE-2026-67181/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-67181
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-67181
- OSV: https://osv.dev/vulnerability/CVE-2026-67181

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-67181/
Summaries are generated and may contain mistakes; the official description above is the record.