security/libsodium -- crypto_core_ed25519_is_valid_point mishandles checks for whether an elliptic curve point is valid

Libsodium maintainer reports:

The function crypto_core_ed25519_is_valid_point(), a low-level function used to check if a given elliptic curve point is valid, was supposed to reject points that aren't in the main cryptographic group, but some points were slipping through.

[source]