Netpbm is a package of 220 graphics programs and a programming libraries, including pstopnm. pstopnm is a tool which converts PostScript files to PNM image files.
Max Vozeler reported that pstopnm calls the GhostScript interpreter on untrusted PostScript files without specifying the -dSAFER option, to convert a PostScript file into a PBM, PGM, or PNM file.
An attacker could craft a malicious PostScript file and entice a user to run pstopnm on it, resulting in the execution of arbitrary commands with the permissions of the user running pstopnm.
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