libuv is a multi-platform support library with a focus on asynchronous I/O.
libuv used an incorrect buffer size for paths, causing a buffer overflow.
A remote attacker could possibly execute arbitrary code with the privileges of the process, or cause a Denial of Service condition.
There is no known workaround at this time.
All libuv users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=dev-libs/libuv-1.39.0"