CVE-2013-1987 in libXrender
Summary
by MITRE
Multiple integer overflows in X.org libXrender 0.9.7 and earlier allow X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to the (1) XRenderQueryFilters, (2) XRenderQueryFormats, and (3) XRenderQueryPictIndexValues functions.
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Analysis
by VulDB Data Team • 05/14/2021
The vulnerability identified as CVE-2013-1987 represents a critical security flaw in the X.org libXrender library version 0.9.7 and earlier, which forms a fundamental component of the X Window System used extensively in Unix-like operating systems. This vulnerability manifests through integer overflow conditions that can be exploited by malicious X servers to manipulate memory allocation processes, ultimately leading to buffer overflow conditions that compromise system stability and security. The affected functions specifically target the XRenderQueryFilters, XRenderQueryFormats, and XRenderQueryPictIndexValues operations, which are essential for rendering graphics and managing visual elements within X server environments.
The technical exploitation of this vulnerability occurs when X servers process requests containing maliciously crafted integer values that exceed the maximum limits of the data types used in the affected functions. When these integer overflows occur, they result in incorrect calculations of memory allocation sizes, causing the system to allocate insufficient memory for buffer operations. This insufficient memory allocation creates conditions where subsequent buffer operations can overwrite adjacent memory locations, potentially leading to arbitrary code execution or system crashes. The vulnerability operates at the intersection of multiple CWE categories including CWE-190 for integer overflow and CWE-129 for insufficient boundary checking, making it particularly dangerous in graphical server environments where memory management is critical.
From an operational standpoint, this vulnerability presents significant risks to systems running affected X.org libXrender versions, as it allows attackers to potentially execute arbitrary code with the privileges of the X server process. The impact extends beyond simple system instability to potential privilege escalation scenarios where attackers could leverage the buffer overflow conditions to gain unauthorized access to system resources. The vulnerability is particularly concerning in multi-user environments where multiple X servers might be running simultaneously, as each could potentially serve as an attack vector. The ATT&CK framework categorizes this type of vulnerability under privilege escalation and code execution techniques, with the specific TTPs involving exploitation of memory corruption vulnerabilities in system libraries.
Mitigation strategies for CVE-2013-1987 primarily focus on immediate patching of the affected libXrender library to versions that properly handle integer overflow conditions and implement proper input validation for the affected functions. System administrators should prioritize updating their X.org implementations to versions that address these integer overflow conditions, typically through patch releases or full version upgrades. Additionally, implementing network segmentation and access controls to limit X server access can reduce the attack surface, while monitoring for anomalous X server behavior can help detect potential exploitation attempts. The vulnerability highlights the importance of robust input validation and proper integer handling in system libraries, particularly those handling graphics rendering operations where memory allocation and buffer management are critical components of the system architecture.