CVE-2013-4262 in Subversion
Summary
by MITRE
svnwcsub.py in Subversion 1.8.0 before 1.8.3, when using the --pidfile option and running in foreground mode, allows local users to gain privileges via a symlink attack on the pid file. NOTE: this issue was SPLIT due to different affected versions (ADT3). The irkerbridge.py issue is covered by CVE-2013-7393.
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Analysis
by VulDB Data Team • 05/24/2021
The vulnerability identified as CVE-2013-4262 affects Subversion version 1.8.0 through 1.8.2, specifically when the svnwcsub.py script is executed with the --pidfile option in foreground mode. This flaw represents a privilege escalation vulnerability that exploits a race condition in the pid file creation process. The issue arises from the insecure handling of temporary files and symbolic links during the execution of Subversion's working copy subversion operations. When a user runs the script with a pid file specification, the application creates a pid file in a location that can be manipulated through symbolic link attacks. This vulnerability falls under the category of insecure temporary file handling as classified by CWE-377, where the application creates temporary files with predictable names or locations that can be exploited by local attackers.
The technical mechanism of exploitation involves a classic symlink attack pattern where a local attacker creates a symbolic link with the same name as the pid file that Subversion intends to create. When the svnwcsub.py script executes with the --pidfile option, it attempts to write to the specified pid file location without proper validation of the target file's existence or type. The attacker can place a symbolic link in the expected pid file location that points to a sensitive system file or a location where the attacker has write access. This creates a race condition where the attacker controls the file that gets written to during the pid file creation process, potentially allowing privilege escalation or arbitrary file modification. The vulnerability is particularly dangerous because it operates in foreground mode where the process runs with elevated privileges and can be manipulated by local users who have access to the system.
The operational impact of this vulnerability extends beyond simple privilege escalation as it can be leveraged to compromise the integrity of the Subversion working copy management system. Attackers can potentially modify critical system files or create backdoors through the compromised pid file handling mechanism. This vulnerability affects systems where Subversion is used in environments where local users might have access to the system but should not have elevated privileges. The attack requires local system access and knowledge of the specific Subversion command structure, but once exploited, it can provide attackers with elevated privileges or persistent access to the system. The vulnerability has been classified under the MITRE ATT&CK framework as a privilege escalation technique through insecure file handling and process manipulation, specifically related to the T1548.001 technique for Abuse of Windows Subsystem for Linux or similar privilege escalation methods.
The mitigation strategy for CVE-2013-4262 involves upgrading to Subversion version 1.8.3 or later, where the pid file handling has been corrected to prevent symbolic link attacks. System administrators should ensure that all Subversion installations are updated to the patched versions and verify that the --pidfile option is not used in insecure configurations. Organizations should also implement proper file system permissions and access controls to limit local user access to sensitive system locations where pid files might be created. The fix typically involves implementing proper validation of file targets before writing to them, using atomic file creation methods, and ensuring that temporary files are created with appropriate permissions and in secure locations. Additionally, system monitoring should be implemented to detect suspicious file creation patterns or unauthorized access attempts to pid file locations, particularly in environments where Subversion is used with elevated privileges. The vulnerability highlights the importance of secure coding practices and proper input validation when dealing with temporary file operations in system administration tools.