The GNU C library is the standard C library used by Gentoo Linux systems.
Multiple vulnerabilities have been discovered in the GNU C Library:
Please review the CVEs referenced below for additional vulnerabilities that had already been fixed in previous versions of sys-libs/glibc, for which we have not issued a GLSA before.
A remote attacker could exploit any application which performs host name resolution using getaddrinfo() in order to execute arbitrary code or crash the application. The other vulnerabilities can possibly be exploited to cause a Denial of Service or leak information.
A number of mitigating factors for CVE-2015-7547 have been identified. Please review the upstream advisory and references below.
All GNU C Library users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=sys-libs/glibc-2.21-r2"
It is important to ensure that no running process uses the old glibc anymore. The easiest way to achieve that is by rebooting the machine after updating the sys-libs/glibc package.
Note: Should you run into compilation failures while updating, please see bug 574948.