pmake is Debian’s version of NetBSD’s make, a tool to build programs in parallel.
/usr/share/mk/bsd.lib.mk and /usr/share/mk/bsd.prog.mk create temporary files insecurely, with predictable names (/tmp/_depend[PID]), and without using $TMPDIR.
The make include files allow local users to overwrite arbitrary files via a symlink attack.
There is no known workaround at this time.
All pmake users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=sys-devel/pmake-1.111.3.1"