October 27, 2016

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(LiveHacking.Com) – Unlike many Linux distributions, which are superseded almost daily, stable distributions from RedHat, CentOS and the Ubuntu LTS (Long Term Support) variants offer stability and a longer supported lifetime.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

Canonical and others close kernel holes

Canonical has released updated kernels for Ubuntu versions 10.04 LTS, 9.10, 9.04, 8.04 LTS and 6.06 LTS to close the recently discovered holes in the Linux kernel. The updates are also for the equivalent versions of Kubuntu, Edubuntu and Xubuntu and should be available through Ubuntu’s Software Update system.

Read the full article here.