In Libgcrypt before 1.7.7, an attacker who learns the EdDSA session key (from side-channel observation during the signing process) can easily recover the long-term secret key. 1.7.7 makes a cipher/ecc-eddsa.c change to store this session key in secure memory, to ensure that constant-time point operations are used in the MPI library.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:HI:NA:N5.9/CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N