CVE-2006-1017 in PHP
Summary
by MITRE
The c-client library 2000, 2001, or 2004 for PHP before 4.4.4 and 5.x before 5.1.5 do not check the (1) safe_mode or (2) open_basedir functions, and when used in applications that accept user-controlled input for the mailbox argument to the imap_open function, allow remote attackers to obtain access to an IMAP stream data structure and conduct unauthorized IMAP actions.
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Analysis
by VulDB Data Team • 08/18/2006
The c-client library vulnerability identified as CVE-2006-1017 represents a critical security flaw in PHP's IMAP functionality that persisted across multiple versions of the PHP runtime environment. This vulnerability specifically affects PHP versions prior to 4.4.4 and 5.1.5, where the c-client library implementation failed to properly enforce security boundaries that are fundamental to preventing unauthorized access to system resources. The flaw manifests when applications utilize the imap_open function with user-controllable mailbox arguments, creating a pathway for malicious actors to bypass critical security controls that should otherwise protect system integrity.
The technical root cause of this vulnerability stems from the absence of proper validation mechanisms within the c-client library implementation. When PHP applications process mailbox parameters through the imap_open function, the library should verify that the specified mailbox location adheres to the safe_mode and open_basedir restrictions that are standard security measures in PHP environments. However, the vulnerable versions of the c-client library completely disregard these security checks, allowing attackers to manipulate the mailbox argument in ways that could expose underlying IMAP stream data structures. This failure to validate user input creates an attack surface where remote adversaries can execute unauthorized IMAP operations against systems they otherwise shouldn't be able to access.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it enables attackers to conduct unauthorized IMAP actions that can compromise email server integrity and confidentiality. When an attacker successfully exploits this vulnerability, they gain access to IMAP stream data structures that contain sensitive information about email accounts, server configurations, and potentially user credentials. This access can lead to unauthorized email reading, message manipulation, account enumeration, and other malicious activities that can severely impact organizational security. The vulnerability particularly affects web applications that process user input for IMAP connections, making it a significant concern for email-based services and applications that rely on PHP's IMAP functionality for email management.
This vulnerability aligns with CWE-20, which describes improper input validation, and represents a classic example of how insufficient security controls in library implementations can create systemic risks for entire application ecosystems. The ATT&CK framework categorizes this issue under privilege escalation and defense evasion techniques, as attackers can leverage this vulnerability to gain elevated access to system resources while bypassing standard security controls. Organizations running vulnerable PHP versions should implement immediate mitigations including upgrading to patched PHP versions, implementing proper input validation for IMAP operations, and configuring restrictive safe_mode and open_basedir settings to prevent exploitation. Additionally, network segmentation and monitoring of IMAP traffic can help detect and prevent unauthorized access attempts that may exploit this vulnerability.