RUSTSEC-2026-0258: h2 unbounded empty DATA frames

What to do

1. See which version you have: cargo tree -i h2 (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p h2. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example h2 = "0.4.16") 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

The h2 crate, used internally by hyper, had a flaw that would accept and queue empty DATA frames without limit. If streams were not actively drained, this could lead to unbounded memory usage, or a panic if the length overflows.

Low severity.

Patched in v0.4.16.

References

• Package: crates.io/crates/h2
• Advisory: rustsec.org/advisories/RUSTSEC-2026-0258.html
• Web: github.com/hyperium/h2/pull/935

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 h2

• VulnerabilityRUSTSEC-2023-0034 · 2023-04-14Resource exhaustion vulnerability in h2 may lead to Denial of Service (DoS)
• VulnerabilityRUSTSEC-2024-0003 · 2024-01-17Resource exhaustion vulnerability in h2 may lead to Denial of Service (DoS)
• VulnerabilityRUSTSEC-2024-0332 · 2024-04-03Degradation of service in h2 servers with CONTINUATION Flood

Full security history of h2