Vulnerability Note VU#470151

Linux Kernel local privilege escalation via SUID /proc/pid/mem write

Overview

Linux kernel >= 2.6.39 incorrectly handles the permissions for /proc/<pid>/mem. A local, authenticated attacker could exploit this vulnerability to escalate to root privileges. Exploit code is available in the wild and there have been reports of active exploitation.

I. Description

/proc/<pid>/mem is an interface for reading and writing to process memory. The protections to protect unprivileged users from writing to process memory were found to be insufficient and have resulted in exploitation of the interface. By writing to the memory of a suid process, an attacker can run arbitrary code with root privileges. Further technical details can be found on Jason A. Donenfeld's ZX2C4 blog post.

II. Impact

A local, authenticated attacker may be able to gain root privileges on the system.

III. Solution

Apply an update

Patch commit e268337dfe26dfc7efd422a804dbb27977a3cccc has been provided by Linus Torvalds to address this vulnerability. Kernel image 3.0.18 and 3.2.2 have included this commit so far.

Users who obtain the Linux kernel from a third-party vendor, such as their operating system vendor, should see the vendor information portion of this document for a partial list of affected vendors.

Vendor Information

Vendor	Status	Date Notified	Date Updated
CentOS	Affected		2012-01-27
Debian GNU/Linux	Not Affected		2012-01-27
Gentoo Linux	Unknown		2012-01-27
Red Hat, Inc.	Affected		2012-01-27
Slackware Linux Inc.	Unknown		2012-01-27
SUSE Linux	Unknown		2012-01-27
Ubuntu	Affected		2012-01-27

References

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=e268337dfe26dfc7efd422a804dbb27977a3cccc
http://blog.zx2c4.com/749
http://www.outflux.net/blog/archives/2012/01/22/fixing-vulnerabilities-with-systemtap/

Credit

Jüri Aedla reported this vulnerability to the Linux kernel developers.

This document was written by Jared Allar.

Other Information

Date Public:	2012-01-17
Date First Published:	2012-01-27
Date Last Updated:	2012-01-27
CERT Advisory:
CVE-ID(s):	CVE-2012-0056
NVD-ID(s):	CVE-2012-0056
US-CERT Technical Alerts:
Severity Metric:	15.32
Document Revision:	11

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