RUSTSEC-2026-0069: Incorrect Length Encoding on KDF Export

What to do

1. See which version you have: cargo tree -i hpke-rs (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p hpke-rs. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example hpke-rs = "0.6.0") 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

Passing values length > 65535 to Context::export produces output that disagrees with the RFC 9180 label encoding. In particular the length value is cast to u16 truncating any value exceeding 65535.

Impact

Applications that use hpke-rs to export very large secrets would experience interoperability issues with other applications that use a correct implementation to export very large secrets.

Mitigation

Starting with version 0.6.0, an error will be returned when attempting to call Context::export with an output length > 65535.

References

• Package: crates.io/crates/hpke-rs
• Advisory: rustsec.org/advisories/RUSTSEC-2026-0069.html
• Web: github.com/cryspen/hpke-rs/pull/128

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 hpke-rs

• VulnerabilityRUSTSEC-2026-0070 · 2026-02-11Panic When Opening or Sealing on Export-Only Context
• VulnerabilityRUSTSEC-2026-0071 · 2026-02-05Nonce Reuse in HPKE Context

Full security history of hpke-rs