Mercury MR804 Router 8.0 3.8.1 Build 101220 Rel.53006nB allows remote attackers to cause a denial of service (service hang) via a crafted string in HTTP header fields such as (1) If-Modified-Since, (2) If-None-Match, or (3) If-Unmodified-Since.  NOTE: some of these details are obtained from third party information.