nimiq-keys: Denial of service in Ed25519 multisig delinearization via invalid curve points

Impact

A denial-of-service vulnerability exists in the Ed25519 multisig delinearization code path. Ed25519PublicKey::delinearize() in keys/src/multisig/mod.rs called .unwrap() on curve point decompression, which panics when a public key is
constructed from 32 bytes that do not represent a valid point on the Ed25519 curve. Ed25519PublicKey construction only validates byte length, not curve membership, so invalid keys can reach the delinearization path and crash the
hosting process.

A secondary panic existed in Commitment::From<[u8; 32]>, which similarly called .unwrap() on a failing curve point decompression.

Who is affected: Browser and desktop wallet users of the web-client WASM library and the nimiq-wallet crate, when initiating a multisig operation with an attacker-supplied public key. An attacker must convince the user to include
a crafted public key in a multisig setup — this is not a remotely triggerable node/validator crash.

Who is NOT affected: Validator nodes, consensus, blockchain, mempool, and networking code. There is no on-chain multisig account type; multisig is a purely client-side construct, and no validator/consensus code calls the multisig delinearization path.

Patches

See PR.

Workarounds

No code-level workaround exists short of the patch. Users of wallet applications can mitigate exposure by only performing multisig operations with public keys received from trusted sources.

Resources

• Affected code: keys/src/multisig/mod.rs, keys/src/multisig/commitment.rs