CVE-2016-4544 in PHP
Summary
by MITRE
The exif_process_TIFF_in_JPEG function in ext/exif/exif.c in PHP before 5.5.35, 5.6.x before 5.6.21, and 7.x before 7.0.6 does not validate TIFF start data, which allows remote attackers to cause a denial of service (out-of-bounds read) or possibly have unspecified other impact via crafted header data.
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Analysis
by VulDB Data Team • 08/22/2022
The vulnerability identified as CVE-2016-4544 represents a critical security flaw in PHP's EXIF extension that affects multiple versions of the PHP runtime environment. This issue resides within the exif_process_TIFF_in_JPEG function located in ext/exif/exif.c, which processes TIFF metadata embedded within JPEG files. The vulnerability stems from insufficient validation of TIFF start data, creating a pathway for malicious actors to exploit the system through carefully crafted header data. The flaw manifests as an out-of-bounds read condition that can lead to denial of service attacks, making it particularly dangerous in web applications that process user-uploaded images. The vulnerability affects PHP versions prior to 5.5.35, 5.6.21, and 7.0.6, indicating a widespread impact across the PHP ecosystem during that period. This type of vulnerability falls under CWE-125, which describes out-of-bounds read conditions, and represents a classic example of insufficient input validation that can lead to various security consequences.
The technical exploitation of this vulnerability occurs when PHP processes JPEG files containing maliciously crafted TIFF metadata. The exif_process_TIFF_in_JPEG function fails to properly validate the TIFF header data before attempting to parse it, allowing attackers to manipulate the data structure in ways that cause the application to read memory locations outside the intended bounds. This can result in the application crashing due to segmentation faults or accessing invalid memory addresses, leading to a denial of service condition. The impact extends beyond simple service disruption, as the out-of-bounds read may potentially expose sensitive information from memory or allow for more sophisticated exploitation techniques. Attackers can leverage this vulnerability by uploading or submitting JPEG files with malformed TIFF headers, which when processed by PHP's EXIF extension trigger the flawed parsing logic. The vulnerability's potential for unspecified other impacts suggests that in certain circumstances, it could be exploited for information disclosure or even code execution, depending on the specific memory layout and application context.
From an operational perspective, this vulnerability poses significant risks to web applications that handle user-uploaded images, particularly those using PHP with EXIF processing capabilities. The vulnerability can be exploited through various attack vectors including file uploads, image processing APIs, or any application that accepts JPEG files and processes their metadata. Organizations running affected PHP versions are exposed to potential denial of service attacks that can render their web applications unavailable to legitimate users. The vulnerability's impact is particularly severe in high-traffic environments where a single malicious upload can cause cascading failures across multiple application instances. Security teams must consider the broader implications of this vulnerability within their attack surface, as it can be combined with other exploits or used as a foothold for more extensive attacks. The vulnerability aligns with ATT&CK technique T1059.007, which involves the use of scripting, and demonstrates how seemingly benign file processing functionality can become a vector for system compromise.
The recommended mitigation strategy involves immediate patching of affected PHP installations to versions that contain the necessary security fixes. Organizations should prioritize updating their PHP environments to versions 5.5.35, 5.6.21, or 7.0.6, depending on their current version, to eliminate the vulnerability at its source. Additionally, implementing input validation measures can provide defense-in-depth protection, including sanitizing image uploads and limiting file size restrictions to reduce the attack surface. Network-level protections such as web application firewalls can help detect and block malicious file uploads, while monitoring systems should be configured to alert on unusual patterns of image processing activity. Security teams should also consider implementing proper access controls and limiting the functionality of EXIF processing to only trusted users or applications. The vulnerability's resolution demonstrates the importance of maintaining up-to-date software components and the critical nature of timely security patches in preventing exploitation of known vulnerabilities in widely-used software libraries and frameworks.