CVE-2016-5116 in GD Graphics Library
Summary
by MITRE
gd_xbm.c in the GD Graphics Library (aka libgd) before 2.2.0, as used in certain custom PHP 5.5.x configurations, allows context-dependent attackers to obtain sensitive information from process memory or cause a denial of service (stack-based buffer under-read and application crash) via a long name.
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Analysis
by VulDB Data Team • 09/13/2022
The vulnerability identified as CVE-2016-5116 affects the GD Graphics Library version 2.1.1 and earlier, specifically within the gd_xbm.c file responsible for handling X Bitmap format processing. This issue manifests when the library processes XBM files with excessively long names, creating a scenario where attackers can exploit memory access patterns to either extract sensitive data from process memory or trigger application crashes. The vulnerability is particularly concerning because it occurs during the parsing of XBM format files, which are commonly used for image representation in various applications and systems.
The technical flaw stems from inadequate input validation and buffer management within the XBM parsing routine. When processing an XBM file containing a long name field, the library fails to properly bounds-check the input data, leading to a stack-based buffer under-read condition. This occurs because the code attempts to read beyond the allocated memory boundaries when handling the name attribute, causing unpredictable behavior including memory corruption and potential information disclosure. The vulnerability is classified as a context-dependent issue since it requires specific conditions to be met, particularly involving the manipulation of XBM files with extended name fields within systems running affected versions of libgd.
The operational impact of this vulnerability extends across multiple attack vectors and system configurations. Attackers can leverage this weakness to perform information disclosure attacks by reading process memory contents that may contain sensitive data such as cryptographic keys, user credentials, or application state information. Additionally, the buffer under-read condition can be exploited to cause denial of service through application crashes and system instability, potentially disrupting critical services. The vulnerability is particularly dangerous in web server environments where PHP applications may process user-uploaded XBM files, as it could enable remote code execution or complete system compromise depending on the attack surface and system configuration.
This vulnerability aligns with CWE-125, which describes out-of-bounds read conditions in software implementations, and can be categorized under the ATT&CK technique T1059 for executing malicious code through compromised applications. The exploitability of CVE-2016-5116 is enhanced in PHP environments where libgd is integrated as part of the image processing stack, making it a significant concern for web applications that handle image file uploads or processing. Organizations running affected systems should consider implementing immediate mitigations including updating to libgd version 2.2.0 or later, which contains the necessary patches to address the buffer under-read condition through proper input validation and bounds checking mechanisms.
Mitigation strategies for this vulnerability should include comprehensive patch management programs to ensure all affected systems receive the appropriate libgd updates, along with network segmentation and access controls to limit exposure. System administrators should also implement monitoring solutions to detect potential exploitation attempts through anomalous file processing patterns and implement proper input sanitization for all image file handling operations. The vulnerability serves as a reminder of the critical importance of proper memory management and bounds checking in graphics processing libraries, particularly in environments where untrusted input data must be processed without adequate validation mechanisms.