CVE-2011-4566 in PHP
Summary
by MITRE
Integer overflow in the exif_process_IFD_TAG function in exif.c in the exif extension in PHP 5.4.0beta2 on 32-bit platforms allows remote attackers to read the contents of arbitrary memory locations or cause a denial of service via a crafted offset_val value in an EXIF header in a JPEG file, a different vulnerability than CVE-2011-0708.
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Analysis
by VulDB Data Team • 11/26/2021
The vulnerability CVE-2011-4566 represents a critical integer overflow flaw within PHP's exif extension that specifically affects 32-bit platforms running PHP 5.4.0beta2. This issue resides in the exif_process_IFD_TAG function located in the exif.c source file, where improper handling of offset_val values in EXIF headers within JPEG files creates a dangerous condition that can be exploited remotely. The flaw stems from the lack of proper bounds checking when processing integer values that control memory access operations, creating a scenario where attacker-controlled data can manipulate memory addressing calculations. Such vulnerabilities fall under CWE-190, which specifically addresses integer overflow conditions that can lead to memory corruption and arbitrary code execution. The vulnerability is particularly concerning because it allows remote attackers to potentially access arbitrary memory locations, effectively enabling information disclosure attacks where sensitive data from memory could be read and exfiltrated.
The technical implementation of this vulnerability exploits the fundamental weakness in how PHP processes EXIF metadata within JPEG files. When the exif extension parses JPEG headers, it encounters crafted offset_val parameters that, when processed through the exif_process_IFD_TAG function, cause integer overflow conditions. On 32-bit systems, this overflow can result in negative integer values being used as array indices or memory offsets, leading to unpredictable behavior. The attacker can manipulate the EXIF header data within a JPEG file to force these overflow conditions, which then translate into memory read operations at arbitrary locations. This mechanism can be leveraged to either extract sensitive information from memory or cause the application to crash through invalid memory access patterns, making it a dual threat that can enable both information disclosure and denial of service attacks. The vulnerability operates at the intersection of image processing and memory management, creating a unique attack surface that combines file format parsing with low-level memory access controls.
The operational impact of CVE-2011-4566 extends beyond simple denial of service to encompass serious security implications for web applications that process user-uploaded JPEG files. Web servers running PHP applications that accept and process EXIF data from untrusted sources become vulnerable to remote information disclosure attacks, potentially exposing sensitive system information, session data, or application secrets stored in memory. This vulnerability is particularly dangerous in environments where PHP applications handle file uploads from untrusted users, as attackers can craft malicious JPEG files that trigger the integer overflow during the EXif parsing process. The attack vector is straightforward: an attacker uploads a specially crafted JPEG file containing manipulated EXIF headers, and upon processing by the vulnerable PHP application, the integer overflow occurs, potentially revealing memory contents or causing application instability. The vulnerability also aligns with ATT&CK technique T1059.007, which covers the use of remote code execution through application vulnerabilities, though in this case it manifests more specifically as information disclosure through memory access.
Mitigation strategies for CVE-2011-4566 require immediate patching of affected PHP installations to versions that contain proper integer overflow protections in the exif extension. System administrators should ensure that all PHP installations running on 32-bit platforms are updated to patched versions, as the vulnerability specifically targets the 32-bit architecture where integer overflow conditions are more readily exploitable. Additionally, implementing strict input validation and sanitization for uploaded files can provide defense-in-depth measures, though these approaches may not fully prevent exploitation of the underlying vulnerability. Organizations should also consider disabling the exif extension when it is not required for application functionality, as this eliminates the attack surface entirely. The recommended approach includes deploying web application firewalls that can detect and block suspicious EXIF header patterns, implementing file type validation to ensure only properly formatted JPEG files are processed, and conducting regular security assessments of PHP applications to identify potential exposure points. Furthermore, monitoring for unusual memory access patterns or application crashes following file processing activities can help detect exploitation attempts, while maintaining current threat intelligence feeds to stay informed about related vulnerabilities that may compound the risk in similar attack vectors.