Parsec is a cloud-based application for cryptographically secure file sharing. In versions on the 3.x branch prior to 3.6.0, libparsec_crypto, a component of the Parsec application, does not check for weak order point of Curve25519 when compiled with its RustCrypto backend. In practice this means an attacker in a man-in-the-middle position would be able to provide weak order points to both parties in the Diffie-Hellman exchange, resulting in a high probability to for both parties to obtain the same shared key (hence leading to a successful SAS code exchange, misleading both parties into thinking no MITM has occurred) which is also known by the attacker.

Note only Parsec web is impacted (as Parsec desktop uses libparsec_crypto with the libsodium backend). Version 3.6.0 of Parsec patches the issue.