HTTP::Headers::ActionPack versions before 0.10 for Perl allow CPU exhaustion via Accept-Language ranges matched as regular expressions. _la

HTTP::Headers::ActionPack versions before 0.10 for Perl allow CPU exhaustion via Accept-Language ranges matched as regular expressions.

_language_match interpolates each Accept-Language range into the pattern /^$range\-/i without escaping it, so regular expression syntax in the header reaches the regex engine. A 12-byte range such as (a?|b?){26}z backtracks for seconds, and each increment of the quantifier doubles the time. An invalid range such as ( fails to compile.

A remote attacker can exhaust CPU, or make choose_language die, in any application that passes an untrusted Accept-Language header to it.