Vulnerabilities > CVE-2020-15702 - Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in Canonical Apport

047910
CVSS 7.0 - HIGH
Attack vector
LOCAL
Attack complexity
HIGH
Privileges required
LOW
Confidentiality impact
HIGH
Integrity impact
HIGH
Availability impact
HIGH
local
high complexity
canonical
CWE-367

Summary

TOCTOU Race Condition vulnerability in apport allows a local attacker to escalate privileges and execute arbitrary code. An attacker may exit the crashed process and exploit PID recycling to spawn a root process with the same PID as the crashed process, which can then be used to escalate privileges. Fixed in 2.20.1-0ubuntu2.24, 2.20.9 versions prior to 2.20.9-0ubuntu7.16 and 2.20.11 versions prior to 2.20.11-0ubuntu27.6. Was ZDI-CAN-11234.

Vulnerable Configurations

Part Description Count
Application
Canonical
100
OS
Canonical
4

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Leveraging Race Conditions via Symbolic Links
    This attack leverages the use of symbolic links (Symlinks) in order to write to sensitive files. An attacker can create a Symlink link to a target file not otherwise accessible to her. When the privileged program tries to create a temporary file with the same name as the Symlink link, it will actually write to the target file pointed to by the attackers' Symlink link. If the attacker can insert malicious content in the temporary file she will be writing to the sensitive file by using the Symlink. The race occurs because the system checks if the temporary file exists, then creates the file. The attacker would typically create the Symlink during the interval between the check and the creation of the temporary file.
  • Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions
    This attack targets a race condition occurring between the time of check (state) for a resource and the time of use of a resource. The typical example is the file access. The attacker can leverage a file access race condition by "running the race", meaning that he would modify the resource between the first time the target program accesses the file and the time the target program uses the file. During that period of time, the attacker could do something such as replace the file and cause an escalation of privilege.