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

[GLSA]

Gentoo Linux Security Advisory

Title: Linux Kernel: Remote DoS vulnerability with IPTables TCP Handling (GLSA 200407-12)
Severity: high
Exploitable: remote
Date: July 14, 2004
Updated: October 10, 2004
Bug(s): #55694
ID: 200407-12

Synopsis


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.


Background


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: sys-kernel/aa-sources
Vulnerable: < 2.6.5-r5
Unaffected: >= 2.6.5-r5
Unaffected: < 2.6
Architectures: All supported architectures

Package: sys-kernel/ck-sources
Vulnerable: < 2.6.7-r2
Unaffected: >= 2.6.7-r2
Unaffected: < 2.6
Architectures: All supported architectures

Package: sys-kernel/development-sources
Vulnerable: < 2.6.8
Unaffected: >= 2.6.8
Architectures: All supported architectures

Package: sys-kernel/gentoo-dev-sources
Vulnerable: < 2.6.7-r7
Unaffected: >= 2.6.7-r7
Architectures: All supported architectures

Package: sys-kernel/hardened-dev-sources
Vulnerable: < 2.6.7-r1
Unaffected: >= 2.6.7-r1
Architectures: All supported architectures

Package: sys-kernel/hppa-dev-sources
Vulnerable: < 2.6.7_p1-r1
Unaffected: >= 2.6.7_p1-r1
Architectures: All supported architectures

Package: sys-kernel/mips-sources
Vulnerable: < 2.6.4-r4
Unaffected: >= 2.6.4-r4
Unaffected: < 2.6
Architectures: All supported architectures

Package: sys-kernel/mm-sources
Vulnerable: < 2.6.7-r4
Unaffected: >= 2.6.7-r4
Unaffected: < 2.6
Architectures: All supported architectures

Package: sys-kernel/pegasos-dev-sources
Vulnerable: < 2.6.7-r1
Unaffected: >= 2.6.7-r1
Architectures: All supported architectures

Package: sys-kernel/rsbac-dev-sources
Vulnerable: < 2.6.7-r1
Unaffected: >= 2.6.7-r1
Architectures: All supported architectures

Package: sys-kernel/uclinux-sources
Vulnerable: < 2.6.7_p0
Unaffected: >= 2.6.7_p0-r1
Unaffected: < 2.6
Architectures: All supported architectures

Package: sys-kernel/usermode-sources
Vulnerable: < 2.6.6-r2
Unaffected: >= 2.6.6-r2
Unaffected: < 2.6
Architectures: All supported architectures

Package: sys-kernel/win4lin-sources
Vulnerable: < 2.6.7-r1
Unaffected: >= 2.6.7-r1
Unaffected: < 2.6
Architectures: All supported architectures

Package: sys-kernel/xbox-sources
Vulnerable: < 2.6.7-r1
Unaffected: >= 2.6.7-r1
Unaffected: < 2.6
Architectures: All supported architectures


Description


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.


Impact


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.


Workaround


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.


Resolution


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