RUSTSEC-2020-0008: Flaw in hyper allows request smuggling by sending a body in GET requests

What to do

1. See which version you have: cargo tree -i hyper (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p hyper. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example hyper = "0.12.34") or update the dependency that pulls it in.
3. Check again with cargo audit, or paste your Cargo.lock into our Cargo.toml checker.

Details from the advisory

Vulnerable versions of hyper allow GET requests to have bodies, even if there is no Transfer-Encoding or Content-Length header. As per the HTTP 1.1 specification, such requests do not have bodies, so the body will be interpreted as a separate HTTP request.

This allows an attacker who can control the body and method of an HTTP request made by hyper to inject a request with headers that would not otherwise be allowed, as demonstrated by sending a malformed HTTP request from a Substrate runtime. This allows bypassing CORS restrictions. In combination with other vulnerabilities, such as an exploitable web server listening on loopback, it may allow remote code execution.

The flaw was corrected in hyper version 0.12.34.

References

• Package: crates.io/crates/hyper
• Advisory: rustsec.org/advisories/RUSTSEC-2020-0008.html
• Report: github.com/hyperium/hyper/issues/1925

From the RustSec Advisory Database (CC0-1.0) via the OSV export, downloaded Oct 24, 2026. Severity score computed from the published CVSS vector.

Other advisories for hyper

• Vulnerability MediumRUSTSEC-2016-0002 · 2016-05-09HTTPS MitM vulnerability due to lack of hostname verification
• Vulnerability MediumRUSTSEC-2017-0002 · 2017-01-23headers containing newline characters can split messages
• Vulnerability HighRUSTSEC-2021-0020 · 2021-02-05Multiple Transfer-Encoding headers misinterprets request payload
• Vulnerability MediumRUSTSEC-2021-0078 · 2021-07-07Lenient `hyper` header parsing of `Content-Length` could allow request smuggling
• Vulnerability CriticalRUSTSEC-2021-0079 · 2021-07-07Integer overflow in `hyper`'s parsing of the `Transfer-Encoding` header leads to data loss
• UnsoundRUSTSEC-2022-0022 · 2022-05-10Parser creates invalid uninitialized value

Full security history of hyper