DB_LOOKUP in nss_files/files-XXX.c in the Name Service Switch (NSS) in GNU C
Library (aka glibc or libc6) 2.21 and earlier does not properly check if a
file is open, which allows remote attackers to cause a denial of service
(infinite loop) by performing a look-up while the database is iterated over
the database, which triggers the file pointer to be reset.
this is fixed in glibc-2.22, but i don't plan on trying to backport it as it touches a few more files/logic than i'm comfortable with backporting
i've included this in glibc-2.21-r2 now; stabilization is via bug 574880
This issue was resolved and addressed in
GLSA 201602-02 at https://security.gentoo.org/glsa/201602-02
by GLSA coordinator Tobias Heinlein (keytoaster).