CVE-2015-0202 in Subversion
Summary
by MITRE
The mod_dav_svn server in Subversion 1.8.0 through 1.8.11 allows remote attackers to cause a denial of service (memory consumption) via a large number of REPORT requests, which trigger the traversal of FSFS repository nodes.
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Analysis
by VulDB Data Team • 05/02/2022
The vulnerability identified as CVE-2015-0202 affects the mod_dav_svn module within Apache Subversion versions 1.8.0 through 1.8.11, representing a significant denial of service weakness that can be exploited remotely by attackers to consume excessive system memory resources. This issue specifically targets the FSFS (File System File System) repository implementation within the Subversion server architecture, where the vulnerability manifests through the processing of REPORT requests that traverse repository nodes. The flaw exists in the server-side handling of these requests, where the traversal mechanism does not properly limit the number of nodes processed during repository operations, leading to uncontrolled memory consumption that can ultimately crash or render the service unavailable.
The technical implementation of this vulnerability stems from insufficient input validation and resource management within the mod_dav_svn module's REPORT request processing logic. When a remote attacker sends multiple REPORT requests to the affected Subversion server, each request triggers the traversal of FSFS repository nodes without adequate bounds checking or resource limiting mechanisms. This traversal process continues until the system memory is exhausted, causing the server to become unresponsive and preventing legitimate users from accessing the repository. The vulnerability operates at the protocol level, specifically targeting the WebDAV interface that mod_dav_svn provides for Subversion repositories, making it particularly dangerous for environments where repository access is critical for development workflows and version control operations.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire development infrastructure that relies on Subversion for source code management. Organizations using affected versions of Subversion may experience complete repository unavailability, which can halt development activities, prevent code commits, and disrupt continuous integration pipelines that depend on repository access. The memory consumption pattern is particularly concerning because it can be sustained over time, allowing attackers to maintain the denial of service condition without requiring repeated exploitation attempts. This vulnerability affects both the availability and reliability of version control systems, which are fundamental components of software development environments and can have cascading effects on project timelines and team productivity.
Mitigation strategies for CVE-2015-0202 primarily focus on immediate version upgrades to Subversion 1.8.12 or later, where the vulnerability has been addressed through enhanced resource management and bounds checking in the REPORT request processing. Organizations should also implement network-level protections such as rate limiting and connection throttling to prevent excessive REPORT requests from reaching the vulnerable server. Additionally, monitoring systems should be deployed to detect unusual patterns of memory consumption or high request volumes that may indicate exploitation attempts. Security teams should consider implementing firewall rules that restrict access to the mod_dav_svn interface to trusted IP addresses only, while also ensuring that automated systems are configured to handle resource exhaustion gracefully. The vulnerability aligns with CWE-400, which addresses unchecked resource consumption, and maps to ATT&CK technique T1499.004 for resource consumption attacks, emphasizing the importance of proper resource management and access controls in preventing such exploits.