Nettle is a cryptographic library that is designed to fit easily in almost any context: In cryptographic toolkits for object-oriented languages, such as C++, Python, or Pike, in applications like lsh or GnuPG, or even in kernel space.
It was found that nettle’s RSA and DSA decryption code was vulnerable to cache-related side channel attacks.
See the referenced technical paper “Cache Attacks Enable Bulk Key Recovery on the Cloud” below for details.
An attacker could recover the private key from a co-located virtual-machine instance.
There is no known workaround at this time.
All nettle users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=dev-libs/nettle-3.2-r1"