Gnu Privacy Guard (GnuPG or GPG) is popular open source encryption software used by many operating systems from Linux and FreeBSD to Windows and macOS X. The vulnerability resides in thecryptographic library used by GnuPG, which is prone to local FLUSH+RELOAD side-channel attack. The attack allows an attacker to extract the secret crypto key from a system by analyzing the pattern of memory utilization or the electromagnetic outputs of the device that are emitted during the decryption process.
Source: https://thehackernews.com/2017/07/gnupg-libgcrypt-rsa-encryption.html