GHSA-6hfq-h8hq-87mf is a medium-severity (CVSS 4.8) CWE-444 vulnerability in hyper. A fix is available for hyper — see the affected versions and patch details below.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-6hfq-h8hq-87mf by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
hyper🦀hyper🦀hyperReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Summary
hyper's HTTP server code had a flaw that incorrectly understands some requests with multiple transfer-encoding headers to have a chunked payload, when it should have been rejected as illegal. This combined with an upstream HTTP proxy that understands the request payload boundary differently can result in "request smuggling" or "desync attacks".
Vulnerability
The flaw was introduced in https://github.com/hyperium/hyper/commit/26417fc24a7d05df538e0f39239b373c5c3d61f6, released in v0.12.0.
Consider this example request:
POST /yolo HTTP/1.1
Transfer-Encoding: chunked
Transfer-Encoding: cow
This request should be rejected, according to RFC 7230, since it has a Transfer-Encoding header, but after folding, it does not end in chunked. hyper would notice the chunked in the first line, and then check the second line, and thanks to a missing boolean assignment, not set the error condition. hyper would treat the payload as being chunked. By differing from the spec, it is possible to send requests like these to endpoints that have different HTTP implementations, with different interpretations of the payload semantics, and cause "desync attacks".
There are several parts of the spec that must also be checked, and hyper correctly handles all of those. Additionally, hyper's client does not allow sending requests with improper headers, so the misunderstanding cannot be propagated further.
Read more about desync attacks: https://portswigger.net/research/http-desync-attacks-request-smuggling-reborn
Impact
To determine if vulnerable, all these things must be true:
- Using hyper as an HTTP server. The client is not affected.
- Using HTTP/1.1. HTTP/2 does not use
transfer-encoding. - Using a vulnerable HTTP proxy upstream to hyper. If an upstream proxy correctly rejects the illegal transfer-encoding headers, the desync attack cannot succeed. If there is no proxy upstream of hyper, hyper cannot start the desync attack, as the client will repair the headers before forwarding.
Patches
We have released and backported the following patch versions:
- v0.14.3
- v0.13.10
Workarounds
Besides upgrading hyper, you can take the following options:
- Reject requests that contain a
transfer-encodingheader. - Ensure any upstream proxy handles
transfer-encodingcorrectly.
Credits
This issue was initially reported by ZeddYu Lu From Qi An Xin Technology Research Institute.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | hyper | ≥ 0.14.0&&< 0.14.3 | 0.14.3cargo update -p hyper --precise 0.14.3 |
| 🦀crates.io | hyper | ≥ 0.13.0&&< 0.13.10 | 0.13.10cargo update -p hyper --precise 0.13.10 |
| 🦀crates.io | hyper | ≥ 0.12.0&&< 0.12.36 | 0.12.36cargo update -p hyper --precise 0.12.36 |
Affected Products
hyperhyperDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hyper, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update hyper to 0.14.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-6hfq-h8hq-87mf is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is GHSA-6hfq-h8hq-87mf in your dependencies?
Find it across crates.io, including transitive dependencies.