CVE-2011-0715 in Subversion
Summary
by MITRE
The mod_dav_svn module for the Apache HTTP Server, as distributed in Apache Subversion before 1.6.16, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a request that contains a lock token.
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Analysis
by VulDB Data Team • 01/18/2025
The vulnerability identified as CVE-2011-0715 affects the mod_dav_svn module within the Apache HTTP Server ecosystem, specifically impacting Apache Subversion versions prior to 1.6.16. This issue represents a critical denial of service weakness that can be exploited by remote attackers to disrupt the availability of svn services. The vulnerability manifests through a specific request pattern involving lock tokens, which when processed by the affected module trigger unexpected behavior leading to system instability and daemon termination.
The technical flaw resides in the improper handling of lock tokens within the mod_dav_svn module's request processing logic. When a maliciously crafted request containing an invalid or malformed lock token is submitted to an affected Apache server running the svn module, the system attempts to dereference a NULL pointer during the lock token validation process. This NULL pointer dereference occurs because the module fails to properly validate the lock token structure before attempting to access its properties, resulting in an immediate crash of the httpd daemon process. The vulnerability is classified as a NULL pointer dereference under CWE-476, which represents a common programming error where a null pointer is accessed without proper null checks.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader security implications for organizations relying on Apache Subversion for version control operations. Remote attackers can exploit this weakness to repeatedly crash svn daemons, effectively rendering version control services unavailable to legitimate users. This denial of service condition can be particularly damaging in development environments where continuous integration and deployment pipelines depend on stable svn access. The vulnerability affects any system running Apache HTTP Server with mod_dav_svn enabled and configured for svn repository access, making it a widespread concern across development and enterprise environments that utilize subversion for source code management.
Organizations should implement immediate mitigations including upgrading to Apache Subversion version 1.6.16 or later, which contains the necessary patches to address the NULL pointer dereference issue. The fix involves implementing proper input validation for lock tokens before attempting to process them, ensuring that all pointer references are checked for null values prior to dereferencing. System administrators should also consider implementing network-level protections such as rate limiting and access controls to limit the impact of potential exploitation attempts. From a security framework perspective, this vulnerability aligns with ATT&CK technique T1499.004 for network denial of service and demonstrates the importance of proper input validation as outlined in the OWASP Top 10 2021 category A03: Data Exposure. The vulnerability underscores the critical need for thorough testing of module interactions within web servers and emphasizes the importance of maintaining current software versions to protect against known exploits.