CVE-2016-10166 in GD Graphics Library
Summary
by MITRE
Integer underflow in the _gdContributionsAlloc function in gd_interpolation.c in the GD Graphics Library (aka libgd) before 2.2.4 allows remote attackers to have unspecified impact via vectors related to decrementing the u variable.
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Analysis
by VulDB Data Team • 09/08/2020
The vulnerability identified as CVE-2016-10166 represents a critical integer underflow condition within the GD Graphics Library, specifically in the _gdContributionsAlloc function located in gd_interpolation.c. This flaw affects versions prior to 2.2.4 and constitutes a serious security concern that can be exploited remotely by attackers to potentially execute arbitrary code or cause system instability. The vulnerability stems from improper handling of integer values during the decrementing of the u variable, which creates a condition where the integer wraps around to a negative value, leading to unpredictable behavior in memory allocation and processing operations.
The technical nature of this vulnerability aligns with CWE-191, which describes integer underflow conditions where an integer value is decremented below its minimum representable value, resulting in wraparound behavior. This type of flaw typically occurs when developers fail to validate input parameters or check for potential overflow/underflow conditions before performing arithmetic operations. In the context of the GD Graphics Library, this issue manifests during image interpolation operations where the library processes pixel contributions for scaling and transformation tasks. When the u variable becomes negative due to improper decrementing, it can lead to invalid memory access patterns, buffer overflows, or other memory corruption issues that attackers can potentially leverage for exploitation.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it can enable remote code execution under certain conditions. Attackers who can control the input parameters to the affected library functions can manipulate the integer underflow to redirect execution flow or corrupt memory structures. This makes the vulnerability particularly dangerous in web applications or services that utilize the GD Graphics Library for image processing, as attackers could potentially upload malicious images or manipulate image transformation parameters to trigger the vulnerable code path. The unspecified impact mentioned in the CVE description reflects the potential for various security consequences depending on the execution environment and system configuration.
Mitigation strategies for CVE-2016-10166 primarily involve upgrading to GD Graphics Library version 2.2.4 or later, which contains the necessary patches to address the integer underflow condition. System administrators should also implement proper input validation and sanitization measures when processing image data, particularly in web applications that handle user-uploaded content. Additionally, deploying runtime protections such as address space layout randomization and stack canaries can help mitigate potential exploitation attempts. Organizations should conduct thorough vulnerability assessments to identify all systems utilizing affected versions of the library and ensure comprehensive patch management processes are in place to prevent similar issues from occurring in other components of their software stack. The vulnerability demonstrates the importance of rigorous input validation and proper integer handling in graphics processing libraries, as these components often serve as critical infrastructure elements in web applications and multimedia systems.