GLSA 200407-12: Linux Kernel: Remote DoS vulnerability with IPTables TCP Handling

Title:Linux Kernel: Remote DoS vulnerability with IPTables TCP Handling
Bugs: #55694


A flaw has been discovered in 2.6 series Linux kernels that allows an attacker to send a malformed TCP packet, causing the affected kernel to possibly enter an infinite loop and hang the vulnerable machine.


The Linux kernel is responsible for managing the core aspects of a GNU/Linux system, providing an interface for core system applications as well as providing the essential structure and capability to access hardware that is needed for a running system.

Affected packages

Package Vulnerable Unaffected Architecture(s)
sys-kernel/aa-sources < 2.6.5-r5 >= 2.6.5-r5 All supported architectures
sys-kernel/ck-sources < 2.6.7-r2 >= 2.6.7-r2 All supported architectures
sys-kernel/development-sources < 2.6.8 >= 2.6.8 All supported architectures
sys-kernel/gentoo-dev-sources < 2.6.7-r7 >= 2.6.7-r7 All supported architectures
sys-kernel/hardened-dev-sources < 2.6.7-r1 >= 2.6.7-r1 All supported architectures
sys-kernel/hppa-dev-sources < 2.6.7_p1-r1 >= 2.6.7_p1-r1 All supported architectures
sys-kernel/mips-sources < 2.6.4-r4 >= 2.6.4-r4 All supported architectures
sys-kernel/mm-sources < 2.6.7-r4 >= 2.6.7-r4 All supported architectures
sys-kernel/pegasos-dev-sources < 2.6.7-r1 >= 2.6.7-r1 All supported architectures
sys-kernel/rsbac-dev-sources < 2.6.7-r1 >= 2.6.7-r1 All supported architectures
sys-kernel/uclinux-sources < 2.6.7_p0 >= 2.6.7_p0-r1 All supported architectures
sys-kernel/usermode-sources < 2.6.6-r2 >= 2.6.6-r2 All supported architectures
sys-kernel/win4lin-sources < 2.6.7-r1 >= 2.6.7-r1 All supported architectures
sys-kernel/xbox-sources < 2.6.7-r1 >= 2.6.7-r1 All supported architectures


An attacker can utilize an erroneous data type in the IPTables TCP option handling code, which lies in an iterator. By making a TCP packet with a header length larger than 127 bytes, a negative integer would be implied in the iterator.


By sending one malformed packet, the kernel could get stuck in a loop, consuming all of the CPU resources and rendering the machine useless, causing a Denial of Service. This vulnerability requires no local access.


If users do not use the netfilter functionality or do not use any ``--tcp-option'' rules they are not vulnerable to this exploit. Users that are may remove netfilter support from their kernel or may remove any ``--tcp-option'' rules they might be using. However, all users are urged to upgrade their kernels to patched versions.


Users are encouraged to upgrade to the latest available sources for their system:

    # emerge sync
    # emerge -pv your-favorite-sources
    # emerge your-favorite-sources

    # # Follow usual procedure for compiling and installing a kernel.
    # # If you use genkernel, run genkernel as you would do normally.



This GLSA and any updates to it are available for viewing at the Gentoo Security Website:


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