Netpbm is a package of 220 graphics programs and a programming library, including pnmtopng, a tool to convert PNM image files to the PNG format.
RedHat reported that pnmtopng is vulnerable to a buffer overflow.
An attacker could craft a malicious PNM file and entice a user to run pnmtopng on it, potentially resulting in the execution of arbitrary code with the permissions of the user running pnmtopng.
There is no known workaround at this time.
All Netpbm users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose media-libs/netpbm