CVE-2013-1845 in Subversion
Summary
by MITRE
The mod_dav_svn Apache HTTPD server module in Subversion 1.6.x before 1.6.21 and 1.7.0 through 1.7.8 allows remote authenticated users to cause a denial of service (memory consumption) by (1) setting or (2) deleting a large number of properties for a file or directory.
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Analysis
by VulDB Data Team • 01/02/2022
The vulnerability identified as CVE-2013-1845 represents a significant denial of service weakness within the mod_dav_svn Apache HTTPD server module that affects Subversion versions prior to specific patches. This flaw resides in the handling of property operations within the Subversion version control system, specifically when managing file and directory metadata through the WebDAV interface. The issue manifests when authenticated users exploit the module's insufficient validation of property operations, allowing them to manipulate the system's memory allocation patterns in a manner that leads to excessive resource consumption. The vulnerability is particularly concerning because it affects both the 1.6.x and 1.7.x release lines of Subversion, indicating a widespread impact across multiple version branches of the software.
The technical mechanism behind this vulnerability involves the manipulation of Subversion properties through the mod_dav_svn module, which provides WebDAV access to Subversion repositories. When an authenticated user performs operations such as setting or deleting a large number of properties on files or directories, the module fails to properly limit or validate the resource consumption associated with these operations. This allows attackers to cause memory exhaustion through what appears to be legitimate administrative actions. The vulnerability operates at the intersection of WebDAV protocol handling and Subversion's internal property management systems, creating a scenario where normal user operations can be weaponized to consume system resources. The flaw demonstrates poor input validation and resource management practices that are classified under CWE-400, which specifically addresses "Uncontrolled Resource Consumption" in software systems. The vulnerability affects the module's ability to properly track and limit memory allocation during property operations, leading to progressive memory exhaustion that can ultimately render the server unavailable to legitimate users.
From an operational perspective, this vulnerability creates a substantial risk for organizations that rely on Subversion repositories accessible through WebDAV interfaces. The impact extends beyond simple service disruption to potentially affecting business continuity and operational availability of version control systems. Attackers can exploit this weakness without requiring special privileges beyond authentication, making it particularly dangerous in environments where multiple users have access to repository operations. The memory consumption pattern associated with this vulnerability can be difficult to detect in real-time monitoring systems, as the resource exhaustion occurs gradually and may not immediately trigger alerts. This makes the vulnerability particularly insidious because it can remain undetected while slowly degrading system performance until complete service disruption occurs. The attack vector is particularly relevant in enterprise environments where Subversion repositories serve as central points of collaboration and version management, potentially affecting development workflows and software delivery processes.
The mitigation strategy for CVE-2013-1845 involves immediate patching of affected Subversion installations to versions 1.6.21 or 1.7.8 and later, which contain the necessary fixes for property handling and resource management. Organizations should implement monitoring systems that track property operations and memory consumption patterns to detect anomalous usage that might indicate exploitation attempts. Network segmentation and access controls should be strengthened to limit the number of authenticated users who can perform property operations on critical repositories. The fix addresses the root cause by implementing proper bounds checking and resource limiting mechanisms within the mod_dav_svn module, preventing unbounded memory allocation during property operations. Security teams should also consider implementing rate limiting and resource quotas for repository operations to provide additional protection against similar vulnerabilities. This vulnerability aligns with ATT&CK technique T1499.004, which covers "Toggle Service" and resource exhaustion attacks, and demonstrates how seemingly benign administrative functions can be exploited for denial of service purposes. Organizations should also review their overall security posture and implement comprehensive monitoring for resource consumption anomalies that could indicate similar vulnerabilities in other modules or systems.