RUSTSEC-2016-0002: HTTPS MitM vulnerability due to lack of hostname verification

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 = "0.9.4") 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

When used on Windows platforms, all versions of Hyper prior to 0.9.4 did not perform hostname verification when making HTTPS requests.

This allows an attacker to perform MitM attacks by preventing any valid CA-issued certificate, even if there's a hostname mismatch.

The problem was addressed by leveraging rust-openssl's built-in support for hostname verification.

References

• Package: crates.io/crates/hyper
• Advisory: rustsec.org/advisories/RUSTSEC-2016-0002.html
• Web: github.com/hyperium/hyper/blob/master/CHANGELOG.md#v094-2016-05-09

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-2017-0002 · 2017-01-23headers containing newline characters can split messages
• Vulnerability CriticalRUSTSEC-2020-0008 · 2020-03-19Flaw in hyper allows request smuggling by sending a body in GET requests
• 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