Linux Kernel 2.6.38 Remote NULL Pointer Dereference ==================================================== [Advisory Information] Title: Linux kernel 2.6.38: Remote NULL pointer dereference Release date: 11/05/2011 Last update: 11/05/2011 Credits: Aristide Fattori, Università degli Studi di Milano (joystick@security.dico.unimi.it) Roberto Paleari, Emaze Networks S.p.A (roberto.paleari@emaze.net) [Vulnerability Information] Class: Remote NULL pointer dereference CVE: [Affected Software] We confirm the presence of this vulnerability in the following kernel versions: - Linux kernel 2.6.38.6 (vanilla) - Linux kernel 2.6.38.4 (vanilla) - Linux kernel 2.6.38.3 (vanilla) - Debian kernel image 2.6.38-2-686 Other Linux kernel versions could be also affected by this issue. [Vulnerability Details] In function icmp_send() (net/ipv4/icmp.c), the parameter passed to dev_net() function is not properly validated. This can lead to a NULL pointer dereference that crashes the kernel. An attacker can exploit this bug and cause a DoS, both on a specific target or on any 2.6.38.x machine connected to the local network. To cause the crash, the attacker must flood the target with fragmented IPv4 packets. Important fields in the IP packet are: * Flags: the MF flag must be set. * Fragment ID: using pseudo-random values for this field quickly fills fragmented queues in the victim's kernel, as it is unable to easily reassemble received packets. * TOS: using pseudo-random values for this field trigger the creation of more than one route cache entry for the same destination address, increasing the chances of incurring in the error condition described before. Other fields of the packet do not really matter, and they can be set to arbitrary values. [Report Timeline] * 10/05/2011 - Vendor informed * 10/05/2011 - Vendor asked to publicly disclose the details of this issue [Disclaimer] The authors, Emaze Networks S.p.A and Università degli Studi di Milano are not responsible for the misuse of the information provided in their security advisories. These advisories are a service to the professional security community. There are NO WARRANTIES with regard to this information. Any application or distribution of this information constitutes acceptance AS IS, at the user's own risk. This information is subject to change without notice.