CVE-2002-2214 in PHP
Summary
by MITRE
The php_if_imap_mime_header_decode function in the IMAP functionality in PHP before 4.2.2 allows remote attackers to cause a denial of service (crash) via an e-mail header with a long "To" header.
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Analysis
by VulDB Data Team • 06/23/2019
The vulnerability identified as CVE-2002-2214 represents a critical denial of service flaw within PHP's IMAP functionality that existed in versions prior to 4.2.2. This issue specifically targets the php_if_imap_mime_header_decode function which processes email headers when PHP interacts with IMAP mail servers. The vulnerability stems from inadequate input validation and buffer handling mechanisms within the MIME header decoding process, creating an exploitable condition that can be triggered by malformed email headers.
The technical exploitation of this vulnerability occurs when a remote attacker crafts an email message containing an excessively long "To" header field that exceeds the allocated buffer space within PHP's IMAP processing module. When the php_if_imap_mime_header_decode function attempts to parse this malformed header, it fails to properly handle the buffer overflow condition, resulting in a crash of the PHP process or the entire web server instance. This behavior manifests as an immediate denial of service condition that prevents legitimate users from accessing services that depend on PHP's mail handling capabilities.
From an operational impact perspective, this vulnerability poses significant risks to web applications that utilize PHP's IMAP functionality for email processing, particularly those serving as mail servers, email clients, or applications that process incoming email messages through IMAP protocols. The crash condition can affect not only individual PHP processes but potentially entire server instances, leading to service interruptions that may last until manual intervention or system restart occurs. This vulnerability is particularly dangerous in environments where PHP applications handle large volumes of email traffic or where automated email processing systems are in place.
The vulnerability maps to CWE-121, which describes heap-based buffer overflow conditions, and aligns with ATT&CK technique T1499.004 related to network denial of service attacks. Organizations using affected PHP versions should implement immediate mitigations including upgrading to PHP 4.2.2 or later, which contains the necessary patches to properly handle buffer boundaries during MIME header decoding. Additional protective measures include implementing email filtering mechanisms that sanitize header fields before processing, configuring input validation for email headers, and monitoring for unusual patterns of email processing failures that might indicate exploitation attempts.
Security practitioners should also consider implementing network-level protections such as rate limiting for email processing endpoints and configuring intrusion detection systems to monitor for patterns consistent with this specific vulnerability. The patch for this vulnerability addresses the root cause by implementing proper buffer size checking and memory allocation handling within the IMAP header decoding function, preventing the overflow condition that previously led to process crashes and system instability. Regular security assessments and vulnerability scanning should include verification of PHP version compliance to prevent similar issues from affecting operational environments.