Libgcrypt is a general purpose cryptographic library derived out of GnuPG.
A vulnerability in the implementation of ElGamal decryption procedures of Libgcrypt leaks information to various side-channels.
A physical side-channel attack allows a remote attacker to fully extract decryption keys during the decryption of a chosen ciphertext.
There is no known workaround at this time.
All Libgcrypt users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=dev-libs/libgcrypt-1.5.4"