CVE-2013-7328 in PHP
Summary
by MITRE
Multiple integer signedness errors in the gdImageCrop function in ext/gd/gd.c in PHP 5.5.x before 5.5.9 allow remote attackers to cause a denial of service (application crash) or obtain sensitive information via an imagecrop function call with a negative value for the (1) x or (2) y dimension, a different vulnerability than CVE-2013-7226.
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Analysis
by VulDB Data Team • 02/01/2022
The vulnerability identified as CVE-2013-7328 represents a critical security flaw in PHP's gd library implementation that affects versions prior to 5.5.9. This issue manifests within the gdImageCrop function located in the ext/gd/gd.c source file, where multiple integer signedness errors create exploitable conditions that can be leveraged by remote attackers to compromise system integrity. The vulnerability specifically targets the imagecrop function which processes image cropping operations, making it particularly dangerous in web applications that handle user-uploaded images or process external image data through PHP's gd extension.
The technical root cause of this vulnerability stems from improper handling of integer values during image processing operations. When the imagecrop function receives negative values for either the x or y dimension parameters, the signedness errors in the gd library's integer arithmetic cause unpredictable behavior in memory management and buffer calculations. These signedness issues occur because the code does not properly validate or convert the signed integer inputs before performing operations that expect unsigned values, leading to scenarios where negative coordinates can cause memory access violations or data corruption. The vulnerability operates through the standard PHP image processing pipeline where user-supplied image parameters are passed directly to the underlying gd library without adequate sanitization, creating a direct path for exploitation.
The operational impact of CVE-2013-7328 extends beyond simple denial of service to potentially expose sensitive system information. Remote attackers can trigger application crashes that result in service disruption, but more critically, the integer signedness errors may allow information disclosure through memory corruption that could reveal stack contents, heap data, or other sensitive information. This vulnerability affects web applications that process user-uploaded images or dynamically generate images through PHP's gd extension, particularly those that do not properly validate image parameters before passing them to the imagecrop function. The attack vector requires minimal privileges as it can be executed through standard web requests, making it highly exploitable in environments where PHP applications handle image processing operations.
Organizations affected by this vulnerability should prioritize immediate patching of PHP installations to version 5.5.9 or later, which contains the necessary fixes for the integer signedness errors in the gdImageCrop function. System administrators should implement input validation measures at the application level to reject negative coordinate values before they reach the gd library functions, though this approach should be considered a temporary mitigation rather than a permanent solution. Security monitoring should be enhanced to detect unusual patterns in image processing operations that might indicate exploitation attempts, and network segmentation should be considered to limit the potential impact of successful attacks. The vulnerability aligns with CWE-190, Integer Overflow or Wraparound, and CWE-191, Integer Underflow, while also mapping to ATT&CK technique T1059.007 for the execution of malicious code through web application vulnerabilities, making it a significant concern for organizations maintaining web infrastructure that processes image data through PHP applications.