CVE-2013-2254 in Sling
Summary
by MITRE
The deepGetOrCreateNode function in impl/operations/AbstractCreateOperation.java in org.apache.sling.servlets.post.bundle 2.2.0 and 2.3.0 in Apache Sling does not properly handle a NULL value that returned when the session does not have permissions to the root node, which allows remote attackers to cause a denial of service (infinite loop) via unspecified vectors.
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Analysis
by VulDB Data Team • 05/03/2019
The vulnerability identified as CVE-2013-2254 resides within the Apache Sling content management platform, specifically in the deepGetOrCreateNode function located in the AbstractCreateOperation.java file within the servlets.post.bundle module. This flaw affects versions 2.2.0 and 2.3.0 of the affected component and represents a critical security issue that can be exploited by remote attackers to cause denial of service conditions. The vulnerability stems from improper handling of null values that occur when a session lacks the necessary permissions to access the root node of the repository structure. When such permission restrictions are encountered during node creation operations, the function fails to properly validate the returned null value, creating a dangerous condition that can lead to infinite loop scenarios.
The technical implementation of this vulnerability demonstrates a classic error handling flaw that falls under CWE-476, which addresses null pointer dereference conditions. In the context of Apache Sling's repository operations, when a user session attempts to create nodes without appropriate permissions to the root node, the system returns a null value that should be properly validated. However, the deepGetOrCreateNode function does not adequately check for this null condition, causing the execution flow to enter an infinite loop where the system repeatedly attempts to process the same null reference without proper termination conditions. This behavior manifests as a denial of service condition where legitimate system resources become consumed indefinitely, preventing normal operational functionality.
From an operational impact perspective, this vulnerability presents a significant risk to Apache Sling applications that rely on the POST servlets for content creation and modification operations. The infinite loop condition created by this flaw can consume substantial CPU resources and memory, effectively rendering the affected system unavailable to legitimate users. Attackers can exploit this vulnerability by crafting specific requests that trigger the permission check scenario, leading to sustained denial of service conditions that can be difficult to detect and mitigate. The vulnerability affects not only individual application availability but also impacts overall system stability and performance, particularly in environments where multiple concurrent operations are expected.
The ATT&CK framework categorizes this vulnerability under the T1499.004 technique for Network Denial of Service, as it enables attackers to consume system resources through malformed requests. Additionally, the vulnerability aligns with T1566.001 for Validating User Input, since the improper handling of null values represents a failure to validate expected return conditions from session permission checks. Organizations using Apache Sling should immediately implement mitigations including updating to patched versions of the servlets.post.bundle component, implementing proper input validation for node creation operations, and configuring appropriate session permissions to prevent unauthorized access attempts that could trigger the vulnerable code path. The recommended remediation strategy involves not only patching the specific code flaw but also establishing robust error handling procedures that properly validate all return values from session and repository operations to prevent similar issues from occurring in other parts of the application stack.