RUSTSEC-2019-0033: Integer Overflow in HeaderMap::reserve() can cause Denial of Service

What to do

1. See which version you have: cargo tree -i http (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p http. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example http = "0.1.20") 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

HeaderMap::reserve() used usize::next_power_of_two() to calculate the increased capacity. However, next_power_of_two() silently overflows to 0 if given a sufficiently large number in release mode.

If the map was not empty when the overflow happens, the library will invoke self.grow(0) and start infinite probing. This allows an attacker who controls the argument to reserve() to cause a potential denial of service (DoS).

The flaw was corrected in 0.1.20 release of http crate.

References

• Package: crates.io/crates/http
• Advisory: rustsec.org/advisories/RUSTSEC-2019-0033.html
• Report: github.com/hyperium/http/issues/352

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 http

• Vulnerability CriticalRUSTSEC-2019-0034 · 2019-11-16HeaderMap::Drain API is unsound

Full security history of http