RUSTSEC-2022-0093: Double Public Key Signing Function Oracle Attack on `ed25519-dalek`

What to do

1. See which version you have: cargo tree -i ed25519-dalek (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p ed25519-dalek. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example ed25519-dalek = "2.0.0") 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

Versions of ed25519-dalek prior to v2.0 model private and public keys as separate types which can be assembled into a Keypair, and also provide APIs for serializing and deserializing 64-byte private/public keypairs.

Such APIs and serializations are inherently unsafe as the public key is one of the inputs used in the deterministic computation of the S part of the signature, but not in the R value. An adversary could somehow use the signing function as an oracle that allows arbitrary public keys as input can obtain two signatures for the same message sharing the same R and only differ on the S part.

Unfortunately, when this happens, one can easily extract the private key.

Revised public APIs in v2.0 of ed25519-dalek do NOT allow a decoupled private/public keypair as signing input, except as part of specially labeled "hazmat" APIs which are clearly labeled as being dangerous if misused.

References

• Package: crates.io/crates/ed25519-dalek
• Advisory: rustsec.org/advisories/RUSTSEC-2022-0093.html
• Web: github.com/MystenLabs/ed25519-unsafe-libs

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