Zero-day vulnerability in Linux kernel

Privilege escalation
CVE-2016-5195

The vulnerability was discovered by security researcher Phil Oester and is called "DIRTY COW".
It is believed that the vulnerability was being exploited in the wild for quite some time.

Vulnerability details

Advisory: SB2016101901 - Privilege escalation in Linux kernel

Vulnerable component: Linux kernel

CVE-ID: CVE-2016-5195

CVSSv3 score: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:H/RL:O/RC:C

CWE-ID: CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Description:

The vulnerability allows a  local user to obtain elevated privileges on the target system.
The weakness is due to race condition in the kernel memory subsystem in the management of copy-on-write operations on read-only memory mappings that lets attackers to overwrite kernel memory and gain kernel-level privileges.
Successful exploitation of the vulnerability results in gaining of root privileges on the vulnerable system.

Note: the vulnerability was being actively exploited.

Public Exploits:

- Linux Kernel 2.6.22 < 3.9 - 'Dirty COW' PTRACE_POKEDATA Race Condition (PoC) (Write Access) [Exploit-DB]

- Linux Kernel 2.6.22 < 3.9 - 'Dirty COW' /proc/self/mem Race Condition Privilege Escalation (/etc/passwd) [Exploit-DB]

- Linux Kernel 2.6.22 < 3.9 - 'Dirty COW' /proc/self/mem Race Condition (PoC) (Write Access) [Exploit-DB]

- Linux Kernel 2.6.22 < 3.9 (x86/x64) - 'Dirty COW' /proc/self/mem Race Condition Privilege Escalation (SUID) [Exploit-DB]

- Linux Kernel 2.6.22 < 3.9 - 'Dirty COW' PTRACE_POKEDATA Race Condition Privilege Escalation (/etc/passwd) [Exploit-DB]

External links:

https://cdn.kernel.org/pub/linux/kernel/v4.x/testing/linux-4.9-rc2.tar.xz
https://dirtycow.ninja/
https://h20566.www2.hpe.com/hpsc/doc/public/display?docId=emr_na-c05352241
https://en.wikipedia.org/wiki/Dirty_COW
http://unix.stackexchange.com/questions/317981/dirty-cow-exploit-cve-2016-5195/318046
https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solut...
http://www.techinformant.in/dirty-cow-cve-2016-5195-vulnerability/
http://thehackernews.com/2016/10/linux-kernel-exploit.html
http://news.softpedia.com/news/linux-kernel-zero-day-cve-2016-5195-patched-after-being-deployed-in-l...
http://securityaffairs.co/wordpress/52521/hacking/dirty-cow-exploit.html
http://www.informationsecuritybuzz.com/expert-comments/dirty-cow-linux-vulnerability/


About zero-day vulnerabilities

Zero-day vulnerability is an undisclosed vulnerability in software that hackers can exploit to compromise computer programs, gain unauthorized access to sensitive data, penetrate networks, etc. We consider vulnerability a zero-day when there is no solution provided from software vendor and the vulnerability is being actively exploited by malicious actors.

Zero-day candidate is a potential zero-day vulnerability in software which might have been used in targeted attacks, however there is no evidence to support this suggestion.