CVE-2019-11041 in PHP
Summary
by MITRE
When PHP EXIF extension is parsing EXIF information from an image, e.g. via exif_read_data() function, in PHP versions 7.1.x below 7.1.31, 7.2.x below 7.2.21 and 7.3.x below 7.3.8 it is possible to supply it with data what will cause it to read past the allocated buffer. This may lead to information disclosure or crash.
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Analysis
by VulDB Data Team • 11/23/2023
The vulnerability identified as CVE-2019-11041 represents a critical buffer overread flaw within PHP's EXIF extension that affects multiple PHP version streams including 7.1.x below 7.1.31, 7.2.x below 7.2.21, and 7.3.x below 7.3.8. This issue stems from improper input validation during the parsing of EXIF metadata from image files, specifically when the exif_read_data() function processes malformed or crafted EXIF data. The vulnerability falls under the CWE-125 weakness category, which specifically addresses out-of-bounds read conditions where an application accesses memory beyond the bounds of a buffer, potentially leading to information disclosure or system instability. The flaw occurs when the EXIF parser fails to properly validate the length of data structures within the EXIF metadata, allowing attackers to craft malicious image files that cause the parser to read beyond allocated memory boundaries.
The operational impact of this vulnerability extends beyond simple crashes to potentially enable information disclosure attacks that can expose sensitive data from the application's memory space. When an attacker supplies specially crafted EXIF data to the exif_read_data() function, the buffer overread can result in the exposure of memory contents including but not limited to session tokens, database credentials, application secrets, or other sensitive information stored in adjacent memory locations. This type of vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter usage, as it can be exploited through web-based interfaces where PHP processes uploaded image files containing malicious EXIF data. The vulnerability can be particularly dangerous in web applications that process user-uploaded images or in systems that parse EXIF data from external sources without proper input sanitization.
Mitigation strategies for CVE-2019-11041 primarily focus on immediate version upgrades to patched PHP releases, with PHP 7.1.31, 7.2.21, and 7.3.8 containing the necessary fixes to prevent the buffer overread condition. Organizations should also implement defensive measures including input validation of all image files before processing, particularly when using the exif_read_data() function, and consider implementing proper error handling to prevent the propagation of malformed data. Additional mitigations include restricting file upload capabilities, implementing content type validation, and employing web application firewalls that can detect and block suspicious EXIF data patterns. The vulnerability demonstrates the importance of proper memory management in interpreted languages and highlights how seemingly benign image processing functions can become attack vectors when proper bounds checking is absent. Security teams should also conduct thorough code reviews to identify other potential buffer overread conditions in similar parsing functions and ensure that all third-party libraries and extensions undergo regular security assessments to prevent similar vulnerabilities from being introduced into production environments.