Bug#1068024:

[Jeffrey Walton]

It looks like more analysis has revealed this is a RCE with the
payload in the modulus of a public key: "The payload is extracted from
the N value (the public key) passed to RSA_public_decrypt, checked
against a simple fingerprint, and decrypted with a fixed ChaCha20 key
before the Ed448 signature verification..." Also see
<https://www.openwall.com/lists/oss-security/2024/03/30/36>.