The BEGIN regular expression in the awk script detector in magic/Magdir/commands in file before 5.15 uses multiple wildcards with unlimited repetitions, which allows context-dependent attackers to cause a denial of service (CPU consumption) via a crafted ASCII file that triggers a large amount of backtracking, as demonstrated via a file with many newline characters.
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=703993
http://www.debian.org/security/2014/dsa-2873