# GHSA-m5ff-3wj3-8ph4: HTTP Request Smuggling: Invalid whitespace characters in headers in Waitress > Attackers can smuggle HTTP requests via invalid whitespace in headers when Waitress is behind a proxy, potentially causing cache poisoning or information disclosure. - **Severity:** Not scored - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 26 Dec 2019 ## What is GHSA-m5ff-3wj3-8ph4? GHSA-m5ff-3wj3-8ph4 is a vulnerability in waitress, published on 26 Dec 2019. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description ### Impact If a proxy server is used in front of waitress, an invalid request may be sent by an attacker that bypasses the front-end and is parsed differently by waitress leading to a potential for HTTP request smuggling. ``` Content-Length: 10 Transfer-Encoding: [\x0b]chunked ``` For clarity: ``` 0x0b == vertical tab ``` Would get parsed by Waitress as being a `chunked` request, but a front-end server would use the `Content-Length` instead as the `Transfer-Encoding` header is considered invalid due to containing invalid characters. If a front-end server does HTTP pipelining to a backend Waitress server this could lead to HTTP request splitting which may lead to potential cache poisoning or unexpected information disclosure. ### Patches Please upgrade to Waitress 1.4.1 which fixes this issue with stricter HTTP field validation. Waitress 1.4.1 due to this change has become much more strict in what is allowed in header values, while the maintainers don't believe that these changes will cause any issues, it may cause failures with non-conformist reverse proxies or clients, and it is highly recommend that users validate the changes in their environment and make sure it won't cause any unacceptable failures. ### Workarounds You may enable additional protections on front-end servers, those that follow RFC7230 correctly would drop the request with a 400 Bad Request. Waitress will now correctly responds to the request with a 400 Bad Request, and will drop the connection to avoid any potential HTTP pipelining issues. ### References This was mentioned in https://portswigger.net/research/http-desync-attacks-what-happened-next and was specifically mentioned as being an issue in HAProxy which did not properly filter it in this article: https://nathandavison.com/blog/haproxy-http-request-smuggling ### Thanks The Pylons Project would like to thank ZeddYu Lu for doing extended testing against Waitress 1.4.0 and bringing this to our attention! ### For more information If you have any questions or comments about this advisory: * open an issue at https://github.com/Pylons/waitress/issues (if not sensitive or security related) * email the Pylons Security mailing list: pylons-project-security@googlegroups.com (if security related) ## Which versions are affected by GHSA-m5ff-3wj3-8ph4? 2 open source packages ship an affected version, including waitress. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `waitress` | PyPI | All versions | 1.4.1 | | `waitress` | PyPI | All versions | 1.4.1 | ## How do I fix GHSA-m5ff-3wj3-8ph4? Upgrade waitress to 1.4.1 or later. ## Is GHSA-m5ff-3wj3-8ph4 being exploited? There is no known exploitation of GHSA-m5ff-3wj3-8ph4 in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for GHSA-m5ff-3wj3-8ph4 and fix it if it is affected. What it is: GHSA-m5ff-3wj3-8ph4 is a vulnerability in waitress, published on 26 Dec 2019. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of GHSA-m5ff-3wj3-8ph4 in the wild and no public exploit code. Affected packages and fixed versions: - waitress (PyPI): affected all versions; fixed in 1.4.1 - waitress (PyPI): affected all versions; fixed in 1.4.1 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/GHSA-m5ff-3wj3-8ph4/ (Markdown: https://insights.sbomify.com/GHSA-m5ff-3wj3-8ph4/index.md) ``` ## Sources - OSV: https://osv.dev/vulnerability/GHSA-m5ff-3wj3-8ph4 --- From sbomify Insights: https://insights.sbomify.com/GHSA-m5ff-3wj3-8ph4/ Summaries are generated and may contain mistakes; the official description above is the record.