CVE-2013-1846 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 (NULL pointer dereference and crash) via a LOCK on an activity URL.
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Analysis
by VulDB Data Team • 01/02/2022
The vulnerability identified as CVE-2013-1846 represents a critical denial of service flaw within the mod_dav_svn Apache HTTPD server module that affects Subversion versions prior to 1.6.21 and 1.7.8. This vulnerability specifically targets the WebDAV implementation within Subversion's Apache module, which enables distributed version control operations through HTTP protocols. The flaw manifests when authenticated remote users exploit a NULL pointer dereference condition during LOCK operations performed on activity URLs, leading to immediate server crashes and service disruption. The vulnerability demonstrates a classic software defect pattern where improper input validation and error handling combine to create a crash condition that can be triggered remotely by authenticated users with appropriate privileges.
The technical implementation of this vulnerability stems from inadequate validation within the mod_dav_svn module's handling of WebDAV LOCK requests targeting activity URLs. When a LOCK operation is performed on an activity URL, the module fails to properly validate the request parameters and subsequently attempts to dereference a NULL pointer in the processing logic. This NULL pointer dereference occurs because the code assumes certain data structures will be properly initialized, but when activity URLs are processed in specific configurations, these assumptions prove incorrect. The vulnerability aligns with CWE-476, which describes NULL pointer dereference conditions, and represents a failure in defensive programming practices where proper null checks and input validation should have been implemented. The flaw exists in the module's request processing pipeline where it fails to validate that required pointers are properly initialized before dereferencing them during the LOCK operation handling.
The operational impact of CVE-2013-1846 extends beyond simple service disruption to potentially compromise the availability of version control systems that rely on Subversion's WebDAV integration. Organizations utilizing Apache HTTPD with mod_dav_svn for their version control infrastructure face significant risk from this vulnerability, as authenticated attackers can systematically crash servers and disrupt development workflows. The attack requires only authenticated access, which may be obtained through legitimate user credentials, making the vulnerability particularly dangerous in environments where access controls are insufficient. This vulnerability can be exploited as part of broader attack campaigns targeting development infrastructure, potentially leading to extended service outages and productivity losses. The impact is exacerbated by the fact that Subversion's WebDAV interface is commonly used in enterprise development environments, making this a high-value target for attackers seeking to disrupt software development processes.
Mitigation strategies for CVE-2013-1846 primarily focus on immediate patching and configuration hardening measures. Organizations should prioritize upgrading to Subversion versions 1.6.21 or 1.7.8 and later, which contain the necessary fixes for the NULL pointer dereference issue. System administrators should also implement network-level access controls to limit who can access the WebDAV endpoints, reducing the attack surface for this vulnerability. The remediation process should include thorough testing of the updated Subversion installations to ensure compatibility with existing workflows and configurations. Additionally, implementing monitoring solutions that can detect unusual LOCK operations or server crash patterns may help identify exploitation attempts. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving service disruption and availability attacks, specifically targeting the availability component of the CIA triad. Organizations should also consider implementing application-level firewalls or intrusion detection systems that can monitor for suspicious WebDAV activity patterns, particularly around LOCK operations on activity URLs. The vulnerability underscores the importance of maintaining up-to-date software components and implementing robust security testing procedures to identify and remediate similar flaws before they can be exploited in production environments.