CVE-2013-1847 in Subversion
Summary
by MITRE
The mod_dav_svn Apache HTTPD server module in Subversion 1.6.0 through 1.6.20 and 1.7.0 through 1.7.8 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via an anonymous LOCK for a URL that does not exist.
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Analysis
by VulDB Data Team • 11/16/2024
The vulnerability identified as CVE-2013-1847 affects the mod_dav_svn Apache HTTPD server module which is part of the Subversion version control system. This issue exists in multiple versions of Subversion including 1.6.0 through 1.6.20 and 1.7.0 through 1.7.8, representing a significant security gap that could impact organizations relying on Apache HTTPD servers with Subversion modules. The vulnerability manifests as a denial of service condition that can be triggered remotely by malicious actors, making it particularly concerning for publicly accessible web servers.
The technical flaw resides in how the mod_dav_svn module handles LOCK requests for URLs that do not exist within the repository. When an anonymous user submits a LOCK request targeting a non-existent resource, the module fails to properly validate the target URL before attempting to process the lock operation. This leads to a NULL pointer dereference condition where the software attempts to access memory locations that have not been properly initialized or allocated. The absence of proper input validation and error handling creates a path where the application crashes when encountering malformed or non-existent resource references during the lock process.
The operational impact of this vulnerability extends beyond simple service disruption as it can be exploited by attackers to repeatedly crash the Apache HTTPD server through carefully crafted LOCK requests. This denial of service condition affects the availability of the Subversion repository, potentially preventing legitimate users from accessing or modifying version-controlled files. Organizations that depend on Subversion for source code management, document control, or collaborative development may experience significant operational disruption when this vulnerability is exploited. The remote nature of the attack means that even systems behind firewalls or with restricted access can be compromised if the Apache server allows anonymous LOCK operations.
The vulnerability aligns with CWE-476 which describes NULL pointer dereference conditions in software applications. From an ATT&CK framework perspective, this represents a denial of service attack pattern that can be classified under technique T1499.3 for network denial of service, where attackers exploit weaknesses in service implementations to disrupt availability. Organizations should implement immediate mitigations including upgrading to patched versions of Subversion, configuring Apache HTTPD to restrict anonymous LOCK operations, and implementing proper input validation for all repository access methods. Additionally, monitoring and logging of LOCK requests should be enhanced to detect potential exploitation attempts, while network segmentation and access controls can help limit the attack surface for vulnerable systems.