CVE-2018-10549 in PHP
Summary
by MITRE
An issue was discovered in PHP before 5.6.36, 7.0.x before 7.0.30, 7.1.x before 7.1.17, and 7.2.x before 7.2.5. exif_read_data in ext/exif/exif.c has an out-of-bounds read for crafted JPEG data because exif_iif_add_value mishandles the case of a MakerNote that lacks a final '\0' character.
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Analysis
by VulDB Data Team • 03/08/2023
The vulnerability identified as CVE-2018-10549 represents a critical out-of-bounds read flaw in PHP's EXIF extension that affects multiple versions of the PHP runtime environment. This issue specifically targets the exif_read_data function within the ext/exif/exif.c file, where improper handling of MakerNote data structures creates conditions for memory access violations. The flaw occurs when processing crafted JPEG files that contain malformed MakerNote entries lacking the expected terminating null character, creating a scenario where the application attempts to read memory beyond the allocated buffer boundaries. This vulnerability falls under the CWE-125 Out-of-bounds Read classification, which is a fundamental memory safety issue that can lead to unpredictable behavior and potential exploitation.
The technical implementation of this vulnerability stems from the exif_iif_add_value function's inadequate validation of MakerNote data structures during EXIF metadata parsing. When the function encounters a MakerNote entry without the proper terminating null character, it continues processing beyond the allocated memory space, resulting in unauthorized memory access patterns. The flaw is particularly dangerous because JPEG files are commonly used in web applications for image uploads and processing, making this vulnerability exploitable through various attack vectors including web-based file uploads and image manipulation scenarios. The vulnerability's impact is amplified by PHP's widespread use in web server environments where image processing is a common operation.
The operational impact of CVE-2018-10549 extends beyond simple application crashes to potentially enable more sophisticated attack vectors. While the immediate effect may manifest as denial of service through segmentation faults or memory corruption, the underlying memory safety issue creates opportunities for attackers to craft malicious JPEG files that could trigger remote code execution under certain conditions. This vulnerability directly maps to ATT&CK technique T1190 - Exploit Public-Facing Application, as it represents a weakness in a widely deployed web application component that processes user-supplied data. The vulnerability affects PHP versions from 5.6.35 and earlier through 7.2.4 and earlier, encompassing a significant portion of production web server environments that rely on PHP for dynamic content generation and media processing.
Mitigation strategies for this vulnerability require immediate patching of affected PHP installations to versions that contain the necessary fixes for proper MakerNote data handling. System administrators should prioritize updating all PHP installations to versions 5.6.36, 7.0.30, 7.1.17, or 7.2.5 respectively, as these releases contain the corrected buffer handling logic. Additional protective measures include implementing strict file type validation for image uploads, sanitizing all user-supplied JPEG data through proper validation routines, and deploying web application firewalls that can detect and block malformed image file requests. Organizations should also consider implementing input validation at multiple layers, including server-side validation of image file headers and content, to prevent exploitation even if the underlying PHP vulnerability remains unpatched. The vulnerability's classification as a memory safety issue makes it particularly important to implement comprehensive memory protection mechanisms and regular security audits of PHP-based applications.