CVE-2012-2138 in Sling
Summary
by MITRE
The @CopyFrom operation in the POST servlet in the org.apache.sling.servlets.post bundle before 2.1.2 in Apache Sling does not prevent attempts to copy an ancestor node to a descendant node, which allows remote attackers to cause a denial of service (infinite loop) via a crafted HTTP request.
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Analysis
by VulDB Data Team • 01/02/2025
The vulnerability identified as CVE-2012-2138 resides within the Apache Sling content management platform, specifically within the org.apache.sling.servlets.post bundle version 2.1.1 and earlier. This flaw manifests in the @CopyFrom operation implementation within the POST servlet, which is responsible for handling HTTP POST requests that perform copy operations within the Sling repository. The vulnerability represents a critical design oversight that enables remote attackers to exploit the system's node traversal logic without proper validation mechanisms.
The technical flaw stems from insufficient boundary checking during node copy operations, allowing malicious actors to craft HTTP requests that attempt to copy an ancestor node to a descendant node within the same repository hierarchy. This creates a circular reference condition where the system enters an infinite loop attempting to process the copy operation, as it cannot properly resolve the relationship between parent and child nodes in the repository structure. The vulnerability specifically affects the POST servlet's handling of the @CopyFrom parameter, which is used to specify the source node for copy operations.
The operational impact of this vulnerability is severe, as it enables remote attackers to execute a denial of service attack against Apache Sling installations. The infinite loop condition consumes system resources continuously, potentially leading to complete system unresponsiveness and service disruption. This type of attack can be executed without authentication requirements, making it particularly dangerous as any remote user can exploit the vulnerability to bring down the affected system. The attack vector is straightforward, requiring only a specially crafted HTTP request that triggers the problematic copy operation logic.
From a cybersecurity perspective, this vulnerability aligns with CWE-835, which describes the weakness of infinite loops in software systems, and relates to the broader category of denial of service vulnerabilities. The ATT&CK framework categorizes this as a resource exhaustion technique, where attackers consume system resources to prevent legitimate use of services. The vulnerability also demonstrates poor input validation practices and inadequate boundary condition checking, which are common patterns in software security flaws. Organizations using Apache Sling should immediately apply the patch version 2.1.2 or later that addresses this specific issue by implementing proper validation of node relationships during copy operations.
Mitigation strategies should include immediate patch deployment to upgrade to Apache Sling bundle version 2.1.2 or higher, which contains the necessary fixes for the copy operation validation. Additionally, organizations should implement network-level filtering to restrict access to the POST servlet endpoints where possible, and establish monitoring mechanisms to detect unusual patterns of copy operations that might indicate exploitation attempts. Regular security assessments of Sling installations should include verification of proper node relationship validation and resource consumption monitoring to prevent similar vulnerabilities from being exploited in the future.