The French Security Incident Response Team issued a security advisory late yesterday described as a “low risk vulnerability” that primarily affects BlackBerry Pearl devices running OS 4.2 and earlier.

A vulnerability has been identified in various BlackBerry devices, which could be exploited by remote attackers to cause a denial of service. This issue is due to an error in the BlackBerry browser that fails to properly handle overly long URLs, which could be exploited by attackers to cause a vulnerable device to become slow or to stop responding by tricking a user into following a specially crafted link.

You can fix this vulnerability simply by upgrading to BlackBerry Device Software version 4.2 Service Pack 1 (4.2.1) which can be found here.