ID CVE-2009-1897
Summary The tun_chr_poll function in drivers/net/tun.c in the tun subsystem in the Linux kernel 2.6.30 and, when the -fno-delete-null-pointer-checks gcc option is omitted, allows local users to gain privileges via vectors involving a NULL pointer dereference and an mmap of /dev/net/tun, a different vulnerability than CVE-2009-1894.
Vulnerable Configurations
  • cpe:2.3:o:linux:linux_kernel:2.6.30:rc7-git6
  • Linux Kernel 2.6.30 Release Candidate 6
  • Linux Kernel 2.6.30 Release Candidate 2
  • Linux Kernel 2.6.30 Release Candidate 3
  • Linux Kernel 2.6.30 Release Candidate 5
  • Linux Kernel 2.6.30
  • Linux Kernel 2.6.30 Release Candidate 1
  • cpe:2.3:o:linux:linux_kernel:2.6.30:rc4:x86_32
  • Linux Kernel
Base: 6.9 (as of 20-07-2009 - 13:37)
  • Buffer Overflow via Environment Variables
    This attack pattern involves causing a buffer overflow through manipulation of environment variables. Once the attacker finds that they can modify an environment variable, they may try to overflow associated buffers. This attack leverages implicit trust often placed in environment variables.
  • Overflow Buffers
    Buffer Overflow attacks target improper or missing bounds checking on buffer operations, typically triggered by input injected by an attacker. As a consequence, an attacker is able to write past the boundaries of allocated buffer regions in memory, causing a program crash or potentially redirection of execution as per the attackers' choice.
  • Client-side Injection-induced Buffer Overflow
    This type of attack exploits a buffer overflow vulnerability in targeted client software through injection of malicious content from a custom-built hostile service.
  • Filter Failure through Buffer Overflow
    In this attack, the idea is to cause an active filter to fail by causing an oversized transaction. An attacker may try to feed overly long input strings to the program in an attempt to overwhelm the filter (by causing a buffer overflow) and hoping that the filter does not fail securely (i.e. the user input is let into the system unfiltered).
  • MIME Conversion
    An attacker exploits a weakness in the MIME conversion routine to cause a buffer overflow and gain control over the mail server machine. The MIME system is designed to allow various different information formats to be interpreted and sent via e-mail. Attack points exist when data are converted to MIME compatible format and back.
  • Overflow Binary Resource File
    An attack of this type exploits a buffer overflow vulnerability in the handling of binary resources. Binary resources may include music files like MP3, image files like JPEG files, and any other binary file. These attacks may pass unnoticed to the client machine through normal usage of files, such as a browser loading a seemingly innocent JPEG file. This can allow the attacker access to the execution stack and execute arbitrary code in the target process. This attack pattern is a variant of standard buffer overflow attacks using an unexpected vector (binary files) to wrap its attack and open up a new attack vector. The attacker is required to either directly serve the binary content to the victim, or place it in a locale like a MP3 sharing application, for the victim to download. The attacker then is notified upon the download or otherwise locates the vulnerability opened up by the buffer overflow.
  • Buffer Overflow via Symbolic Links
    This type of attack leverages the use of symbolic links to cause buffer overflows. An attacker can try to create or manipulate a symbolic link file such that its contents result in out of bounds data. When the target software processes the symbolic link file, it could potentially overflow internal buffers with insufficient bounds checking.
  • Overflow Variables and Tags
    This type of attack leverages the use of tags or variables from a formatted configuration data to cause buffer overflow. The attacker crafts a malicious HTML page or configuration file that includes oversized strings, thus causing an overflow.
  • Buffer Overflow via Parameter Expansion
    In this attack, the target software is given input that the attacker knows will be modified and expanded in size during processing. This attack relies on the target software failing to anticipate that the expanded data may exceed some internal limit, thereby creating a buffer overflow.
  • Buffer Overflow in an API Call
    This attack targets libraries or shared code modules which are vulnerable to buffer overflow attacks. An attacker who has access to an API may try to embed malicious code in the API function call and exploit a buffer overflow vulnerability in the function's implementation. All clients that make use of the code library thus become vulnerable by association. This has a very broad effect on security across a system, usually affecting more than one software process.
  • Buffer Overflow in Local Command-Line Utilities
    This attack targets command-line utilities available in a number of shells. An attacker can leverage a vulnerability found in a command-line utility to escalate privilege to root.
exploit-db via4
description Linux Kernel 2.6.30 'tun_chr_pool()' NULL Pointer Dereference Vulnerability. CVE-2009-1897. Dos exploit for linux platform
id EDB-ID:33088
last seen 2016-02-03
modified 2009-06-17
published 2009-06-17
reporter Christian Borntraeger
title Linux Kernel 2.6.30 - 'tun_chr_pool' NULL Pointer Dereference Vulnerability
refmap via4
  • 20090716 Linux 2.6.30+/SELinux/RHEL5 test kernel 0day, exploiting the unexploitable
  • 20090716 Re: Linux 2.6.30+/SELinux/RHEL5 test kernel 0day, exploiting the unexploitable
  • [linux-kernel] 20090706 Re: PROBLEM: tun/tap crashes if open() /dev/net/tun and then poll() it.
  • [netdev] 20090409 Oops in tun: bisected to Limit amount of queued packets per device
  • [oss-security] 20090717 Linux 2.6.30+/SELinux/RHEL5 test kernel 0day, exploiting the unexploitable
secunia 35839
vupen ADV-2009-1925
xf linux-kernel-tunchrpoll-code-execution(51803)
statements via4
contributor Tomas Hoger
lastmodified 2009-09-02
organization Red Hat
statement Red Hat is aware of this issue and is tracking it via the following bug: The flaw only affects the Red Hat Enterprise Linux 5.4 beta kernel, which includes a backport of the upstream bug fix introducing this flaw (git commit 33dccbb0). This issue did not affect the final released Red Hat Enterprise Linux 5.4 kernel. It is also possible to mitigate this flaw by ensuring that the permissions for /dev/net/tun is restricted to root only. This issue does not affect any other released kernel in any Red Hat product.
Last major update 19-03-2012 - 00:00
Published 20-07-2009 - 13:30
Last modified 16-08-2017 - 21:30
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