MPFR is a library for multiple-precision floating-point computations with exact rounding.
MPFR fails to adequately check user-supplied input, which could lead to 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 MPFR users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=dev-libs/mpfr-3.1.3_p4"