cfg80211 in net/wireless/scan.c in the Linux kernel 2.6.30-rc1 and other versions before 2.6.31-rc6 allows remote attackers to cause a denial of service (crash) via a sequence of beacon frames in which one frame omits an SSID Information Element (IE) and the subsequent frame contains an SSID IE, which triggers a NULL pointer dereference in the cmp_ies function. NOTE: a potential weakness in the is_mesh function was also addressed, but the relevant condition did not exist in the code, so it is not a vulnerability.
git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=cd3468bad96c00b5a512f551674f36776129520e
jon.oberheide.org/files/cfg80211-remote-dos.c
secunia.com/advisories/36278
www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.30.5
www.openwall.com/lists/oss-security/2009/08/17/1
www.openwall.com/lists/oss-security/2009/08/17/2
www.securityfocus.com/bid/36052