Libgcrypt before 1.8.1 does not properly consider Curve25519 side-channel attacks, which makes it easier for attackers to discover a secret key, related to cipher/ecc.c and mpi/ec.c.
https://www.debian.org/security/2017/dsa-3959
https://security-tracker.debian.org/tracker/CVE-2017-0379
https://lists.debian.org/debian-security-announce/2017/msg00221.html
https://eprint.iacr.org/2017/806