CVE-2003-1303 in PHP
Summary
by MITRE
Buffer overflow in the imap_fetch_overview function in the IMAP functionality (php_imap.c) in PHP before 4.3.3 allows remote attackers to cause a denial of service (segmentation fault) and possibly execute arbitrary code via a long e-mail address in a (1) To or (2) From header.
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Analysis
by VulDB Data Team • 09/05/2019
The vulnerability described in CVE-2003-1303 represents a critical buffer overflow flaw within PHP's IMAP functionality that affects versions prior to 4.3.3. This issue resides in the php_imap.c source file within the imap_fetch_overview function, which processes email headers during IMAP operations. The flaw manifests when the system encounters email addresses that exceed predetermined buffer limits in the To or From header fields, creating a condition where memory corruption can occur. The vulnerability is particularly dangerous because it can be exploited remotely without authentication, making it accessible to any attacker who can send specially crafted email messages to a vulnerable PHP application. The buffer overflow occurs due to insufficient bounds checking when processing email header data, allowing attackers to overwrite adjacent memory locations and potentially execute arbitrary code on the affected system.
The technical exploitation of this vulnerability follows a classic buffer overflow pattern where attacker-controlled data exceeds the allocated buffer space in the imap_fetch_overview function. When PHP processes email messages containing excessively long To or From header values, the function fails to validate input length before copying data into fixed-size buffers. This lack of proper input validation creates a condition where memory layout corruption occurs, leading to segmentation faults that can crash the application or potentially allow code execution. The vulnerability maps to CWE-121, which describes stack-based buffer overflow conditions, and also relates to CWE-787, representing out-of-bounds write vulnerabilities. From an operational perspective, this flaw affects web applications that utilize PHP's IMAP functionality to process incoming email messages, particularly those that do not implement proper input sanitization or validation mechanisms.
The operational impact of CVE-2003-1303 extends beyond simple denial of service to include potential remote code execution capabilities that could allow attackers to compromise entire web servers. When exploited successfully, the buffer overflow can lead to segmentation faults that crash the PHP process, causing denial of service for legitimate users, or more severely, allow attackers to inject and execute malicious code with the privileges of the web server process. This vulnerability particularly affects email processing applications, webmail systems, and any PHP-based applications that rely on IMAP functionality for email handling. The attack surface is broad since many web applications use PHP to process email communications, and the vulnerability can be triggered simply by receiving a specially crafted email message. Additionally, this flaw aligns with ATT&CK technique T1190, which describes exploiting vulnerabilities in remote services, and represents a common vector for initial compromise in web application attacks.
Mitigation strategies for CVE-2003-1303 require immediate action including upgrading PHP installations to version 4.3.3 or later, which contains the necessary patches to address the buffer overflow conditions. Organizations should also implement input validation measures that limit the length of email headers processed by PHP applications, particularly in IMAP handling functions. Network-level protections such as email filtering systems can help by sanitizing incoming email headers before they reach vulnerable PHP applications. Security administrators should also consider implementing monitoring solutions that can detect abnormal behavior patterns associated with buffer overflow exploitation attempts. The vulnerability demonstrates the importance of proper input validation and bounds checking in system design, particularly for functions that process untrusted data from external sources. Additionally, organizations should conduct thorough vulnerability assessments to identify other potentially affected components and ensure that all PHP installations are properly patched and maintained according to security best practices.