libuv is a multi-platform support library with a focus on asynchronous I/O.
It was discovered that libuv does not call setgroups before calling setuid/setgid. If this is not called, then even though the uid has been dropped, there may still be groups associated that permit superuser privileges.
Context-dependent attackers could escalate privileges via unspecified vectors.
There is no known workaround at this time.
All libuv users should upgrade to the latest version:
# emerge --sync
# emerge --ask --verbose --oneshot ">=dev-libs/libuv-1.4.2"