Mono provides the necessary software to develop and run .NET client and server applications on various platforms.
IOActive discovered an error in the Mono.Math.BigInteger class, in the reduction step of the Montgomery-based Pow methods, that could lead to a buffer overflow.
A remote attacker could exploit this vulnerability by sending specially crafted data to Mono applications using the BigInteger class, which might lead to the execution of arbitrary code with the privileges of the user running the application (possibly root) or a Denial of Service.
There is no known workaround at this time.
All Mono users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=dev-lang/mono-1.2.5.1-r1"