June 14, 2021

Linux 2.6.39 Memory Handling Vulnerability

(LiveHacking.Com) – Exploits have started appearing that make it possible to gain root privileges on some versions of the Linux kernel due to a flaw in the  /proc/<pid>/mem handling. The vulnerability first came to light when Linus Torvalds released a Linux kernel update last week to fix the flaw and the subsequent analysis of the bug at  Nerdling Sapple.

The bug, which was discovered by Jüri Aedla, allows a local, unprivileged user to escalate their privileges. The problem is that write support to /proc/<pid>/mem was re-enabled in the kernel but with insufficient permissions checking. This means that all Linux kernels >=2.6.39 are vulnerable, up until the fix noted above.

Red Hat have released a small C program which will test a kernel to see if it is vulnerable. If you are not sure if you are running an affected kernel version compile and run the test from https://bugzilla.redhat.com/attachment.cgi?id=556461:

$ gcc -o test test.c
$ ./test

You can read Red Hat’s full security advisory here. Canonical, the makers of Ubuntu Linux, have also announced the release an update for Ubuntu 11.10. The fix can be applied using a standard system update followed by a reboot.

New Kernels for Ubuntu 10.04 LTS Fix Security Vulnerabilities

(LiveHacking.Com) – Unlike many Linux distributions, which are superseded almost daily, stable distributions from RedHat, CentOS and the Ubuntu LTS (Long Term Support) variants offer stability and a longer supported lifetime.

Ubuntu has just issued two new kernels for Ubuntu 10.04 LTS. The 10.04 release, which is available for both the server and the desktop, was released in April 2010 and will be supported until April 2013 (for the desktop) and until April 2015 for the server version.

The first new kernel is 2.6.32-35 a release of the default 2.6.32  kernel that used when Ubuntu 10.04 LTS was first released. The kernel has a number of security related fixes including:

  • The kernel incorrectly handled certain VLAN packets. On some systems, a remote attacker could send specially crafted traffic to crash the system, leading to a denial of service. (CVE-2011-1576)
  • Ecryptfs did not correctly check the origin of mount points. A local attacker could exploit this to trick the system into unmounting arbitrary mount points, leading to a denial of service. (CVE-2011-1833)
  • Taskstats did not enforce access restrictions. A local attacker could exploit this to read certain information, leading to a loss of privacy. (CVE-2011-2494)
  • /proc/PID/io did not enforce access restrictions. A local attacker could exploit this to read certain information, leading to a loss of privacy. (CVE-2011-2495)
  • The Bluetooth stack incorrectly handled certain L2CAP requests. If a system was using Bluetooth, a remote attacker could send specially crafted traffic to crash the system or gain root privileges. (CVE-2011-2497)
  • The EXT4 filesystem contained multiple off-by-one flaws. A local attacker could exploit this to crash the system, leading to a denial of service. (CVE-2011-2695)
  • The IPv6 stack used predictable fragment identification numbers. A remote attacker could exploit this to exhaust network resources, leading to a denial of service. (CVE-2011-2699)
  • The perf command looks for configuration files in the current directory. If a privileged user were tricked into running perf in a directory containing a malicious configuration file, an
  • attacker could run arbitrary commands and possibly gain privileges. (CVE-2011-2905)
  • Long symlinks were incorrectly handled on Be filesystems. A local attacker could exploit this with a malformed Be filesystem and crash the system, leading to a denial of service. (CVE-2011-2928)
  • The kernel incorrectly handled random sequence number generation. An attacker could use this flaw to possibly predict sequence numbers and inject packets. (CVE-2011-3188)
  • The CIFS client incorrectly handled certain large values. A remote attacker with a malicious server could exploit this to crash the system or possibly execute arbitrary code as the root user. (CVE-2011-3191)
The other new kernel, 2.6.38-12, is backport of kernel 2.6.38 from Ubuntu 11.04 to the standard repository. This kernel also contains a number of security updates.

Another zero-day vulnerability in the Windows kernel

Prevx is reporting that an exploit for a previously unknown security vulnerability in Windows’ win32k.sys kernel mode driver has been published on a Chinese forum. The vulnerability allows attackers who have penetrated a system to escalate their privileges.

Read the full story here.


New Rootkit Designed to Attack 64-bit Versions of Windows is in the Wild

Until now there hasn’t been a rootkit which explicitly attacks machines running a 64-bit version of Microsoft Windows. But now the TDL3 rootkit has been updated to infect Windows Vista 64 bit and Windows 7 64 bit.

Rootkits are pieces of malware which infect computers and allow hackers to hide an intrusion and yet  maintain privileged access to a computer by circumventing normal authentication and authorization mechanisms.

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This is a worrying development as 64-bit versions of Windows were considered much more secure than the 32-bit versions because of the various security features which make it more difficult for malware to get into kernel mode.

The 64-bit versions of Windows use two techniques to keep rootkits out of the kernel. First, drivers aren’t allowed access to kernel memory if they aren’t signed with a digital signature (something which malware applications shouldn’t be). Second, Windows 64 bit uses PatchGuard which blocks every kernel mode driver from altering sensitive areas of the kernel.

The new TDL3 rootkit bypasses both PatchGuard and Driver Signature verification by changing the hard drive’s master boot record and intercepts the Windows startup process allowing it to load its own driver. Once the MBR is infected, the rootkit forces a system reboot which bypasses the need for administration level privileges.

How this will develop is yet to be seen, but we are officially now in the era of 64-bit rootkits. You have been warned!

Kernel-level Vulnerability in All versions of the Microsoft Windows

According to TheRegister.co.uk, researchers have identified a kernel-level vulnerability in Windows. This vulnerability allows attackers to gain escalated privileges and may also allow them to remotely execute malicious code. All versions of the Microsoft OS are affected, including Windows 7.

The buffer overflow, which was originally reported, can be exploited to escalate privileges or crash vulnerable machines, IT research company Vupen said. The flaw may also allow attackers to execute arbitrary code with kernel privileges.

Read more about this vulnerability here.