CVE-2019-11036 in PHP
Summary
by MITRE
When processing certain files, PHP EXIF extension in versions 7.1.x below 7.1.29, 7.2.x below 7.2.18 and 7.3.x below 7.3.5 can be caused to read past allocated buffer in exif_process_IFD_TAG function. This may lead to information disclosure or crash.
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Analysis
by VulDB Data Team • 09/12/2023
The vulnerability CVE-2019-11036 represents a critical buffer overread issue within PHP's EXIF extension that affects multiple version streams including 7.1.x below 7.1.29, 7.2.x below 7.2.18, and 7.3.x below 7.3.5. This flaw exists in the exif_process_IFD_TAG function which handles processing of image metadata, particularly when parsing certain malformed or crafted EXIF data within image files. The issue stems from insufficient bounds checking during the parsing of IFD (Image File Directory) tags, allowing an attacker to manipulate the parsing logic to read beyond allocated memory buffers. This vulnerability falls under CWE-129 Improper Validation of Array Index, which specifically addresses the lack of proper validation when accessing array elements or memory regions. The attack vector typically involves uploading or processing specially crafted image files containing malformed EXIF metadata that triggers the buffer overread condition during normal PHP EXIF processing operations.
The technical execution of this vulnerability occurs when PHP's EXIF extension encounters specific patterns in image metadata that cause the exif_process_IFD_TAG function to incorrectly calculate memory boundaries while reading IFD entries. When processing certain image files with malformed EXIF data, the parsing logic can be manipulated to read beyond the intended buffer limits, potentially accessing adjacent memory regions that contain sensitive information such as stack contents, heap data, or other process memory. This overread behavior can result in information disclosure where attackers might extract sensitive data from memory, or alternatively cause a crash leading to denial of service conditions. The vulnerability aligns with ATT&CK technique T1059.007 Command and Scripting Interpreter: Python where attackers might leverage such memory corruption flaws to execute arbitrary code or extract information from vulnerable systems. The impact is particularly severe in web applications that process user-uploaded images, as attackers can craft malicious files that trigger the vulnerability during normal file processing operations.
The operational impact of CVE-2019-11036 extends beyond simple denial of service scenarios to encompass potential information disclosure and system compromise. Web applications that utilize PHP's EXIF extension for image metadata processing become vulnerable to attackers who can upload malicious files to extract memory contents or cause system instability. This vulnerability is particularly dangerous in environments where PHP processes user-uploaded content without proper validation, as it allows for remote exploitation without requiring authentication. The vulnerability can be exploited through various attack chains including web application exploitation, file upload restrictions bypass, and privilege escalation scenarios. Organizations running affected PHP versions face significant risk as the flaw exists in widely used web application frameworks and content management systems that rely on PHP's EXIF processing capabilities. The vulnerability also demonstrates the importance of proper memory management and bounds checking in language extensions, as highlighted in industry standards for secure coding practices.
Mitigation strategies for CVE-2019-11036 primarily focus on immediate version updates to patched PHP releases that address the buffer overread condition in the EXIF extension. System administrators should prioritize upgrading to PHP versions 7.1.29, 7.2.18, or 7.3.5 respectively, which contain the necessary fixes for the exif_process_IFD_TAG function. Additionally, implementing input validation and sanitization for all user-uploaded image files can provide defensive measures against exploitation attempts. Organizations should consider implementing Content Security Policies and restricting image file processing to trusted sources only. Network-level defenses such as web application firewalls can help detect and block malicious file uploads that attempt to exploit this vulnerability. The remediation process should also include thorough testing of the patched environment to ensure that legitimate EXIF processing continues to function properly while preventing the buffer overread conditions. Security monitoring should be enhanced to detect potential exploitation attempts through anomalous file processing patterns or memory access violations that might indicate successful exploitation of this vulnerability.