CVE-2002-2215 in PHP
Summary
by MITRE
The imap_header function in the IMAP functionality for PHP before 4.3.0 allows remote attackers to cause a denial of service via an e-mail message with a large number of "To" addresses, which triggers an error in the rfc822_write_address function.
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Analysis
by VulDB Data Team • 06/28/2021
The vulnerability described in CVE-2002-2215 represents a classic denial of service flaw within PHP's IMAP functionality that existed prior to version 4.3.0. This issue specifically targets the imap_header function which processes email headers when interacting with IMAP servers through PHP applications. The vulnerability arises from insufficient input validation and error handling within the rfc822_write_address function, which is responsible for formatting email addresses according to RFC 822 standards. When an attacker crafts a malicious email message containing an excessive number of "To" addresses, the PHP IMAP implementation fails to properly handle this malformed input, leading to system resource exhaustion and ultimately service disruption.
The technical exploitation of this vulnerability demonstrates a fundamental flaw in how PHP handled email address parsing and formatting within its IMAP extension. The rfc822_write_address function, which is part of the email address handling subsystem, lacks proper bounds checking and recursion limits when processing email headers. When confronted with an email message containing an unusually high number of recipient addresses in the "To" field, the function enters an infinite loop or consumes excessive memory resources, causing the PHP process to become unresponsive. This behavior aligns with CWE-400, which categorizes "Uncontrolled Resource Consumption" as a significant security weakness that can lead to denial of service conditions. The vulnerability operates at the application layer and can be exploited remotely without requiring authentication, making it particularly dangerous for web applications that process email headers from untrusted sources.
The operational impact of CVE-2002-2215 extends beyond simple service disruption to potentially compromise entire web applications and server resources. When exploited, this vulnerability can cause PHP processes to consume all available memory or CPU resources, leading to complete service unavailability for legitimate users. Web applications that rely on PHP's IMAP functionality for email processing become vulnerable to this attack, particularly those that do not implement proper input sanitization or rate limiting measures. The attack vector is straightforward and can be executed through simple email injection techniques, making it accessible to attackers with minimal technical expertise. This vulnerability also relates to ATT&CK technique T1499.004, which covers "Endpoint Denial of Service" through resource exhaustion attacks that target application-level processing functions.
Mitigation strategies for this vulnerability require immediate patching of affected PHP installations to version 4.3.0 or later, where the underlying IMAP handling has been corrected. Organizations should also implement input validation measures that limit the number of addresses processed in email headers, particularly for fields like "To", "Cc", and "Bcc". Network-level defenses can include rate limiting on email processing functions and implementing proper resource monitoring to detect unusual memory or CPU consumption patterns. Additionally, developers should sanitize email header inputs before processing them through PHP's IMAP functions and consider implementing timeouts for email processing operations. The vulnerability serves as a reminder of the importance of robust input validation and error handling in security-critical code sections, particularly in libraries and functions that process untrusted data from external sources. Organizations should also review their email processing workflows to ensure that they implement proper bounds checking and resource management to prevent similar issues from occurring in other components of their email infrastructure.