CVE-2010-2813 in SquirrelMail
Summary
by MITRE
functions/imap_general.php in SquirrelMail before 1.4.21 does not properly handle 8-bit characters in passwords, which allows remote attackers to cause a denial of service (disk consumption) by making many IMAP login attempts with different usernames, leading to the creation of many preferences files.
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Analysis
by VulDB Data Team • 09/23/2021
The vulnerability identified as CVE-2010-2813 affects SquirrelMail versions prior to 1.4.21 and represents a significant denial of service weakness in the IMAP authentication handling mechanism. This flaw specifically targets the functions/imap_general.php file where the application fails to properly sanitize 8-bit character sequences within password inputs during the authentication process. The vulnerability operates through a carefully crafted attack vector that exploits the application's handling of character encoding in authentication contexts, creating a scenario where malicious actors can consume system resources through excessive file creation.
The technical execution of this vulnerability involves leveraging the improper handling of 8-bit characters in password fields to trigger excessive disk usage through the creation of numerous preference files. When remote attackers submit multiple IMAP login attempts with varying usernames and 8-bit character sequences in passwords, the vulnerable SquirrelMail implementation creates individual preference files for each authentication attempt. This behavior stems from the application's failure to normalize or properly validate character encoding in authentication contexts, resulting in a predictable pattern of file system pollution that grows exponentially with each failed login attempt.
From an operational perspective, this vulnerability creates a substantial risk of system resource exhaustion that can lead to complete service disruption. The denial of service attack operates through disk space consumption rather than memory or CPU exhaustion, making it particularly insidious as it can silently consume storage resources over time without immediate detection. The impact is amplified by the fact that attackers can maintain this attack indefinitely, potentially causing system crashes or requiring manual intervention to clear the accumulated preference files. This vulnerability directly maps to CWE-129 and CWE-131 within the Common Weakness Enumeration framework, specifically addressing improper input validation and resource consumption issues.
The attack pattern aligns with several techniques described in the MITRE ATT&CK framework, particularly focusing on resource exhaustion and denial of service tactics. Attackers can leverage this vulnerability to perform sustained attacks against mail servers without requiring sophisticated exploitation techniques, making it accessible to threat actors with minimal technical expertise. The vulnerability demonstrates a classic case of insufficient input sanitization in web applications, where character encoding handling fails to properly validate user-supplied data before processing. Organizations using affected SquirrelMail versions face potential service disruption risks that could impact email availability for legitimate users.
Mitigation strategies for this vulnerability center on upgrading to SquirrelMail version 1.4.21 or later, which includes proper handling of 8-bit characters in authentication contexts. Additionally, administrators should implement rate limiting mechanisms to prevent excessive login attempts that could trigger the vulnerability, along with monitoring systems to detect unusual file creation patterns in preference directories. Network-level protections such as firewall rules that limit authentication attempts from specific IP addresses can provide additional defense in depth. The vulnerability highlights the importance of proper character encoding handling in authentication systems and demonstrates how seemingly minor input validation issues can result in significant operational impacts. Security teams should also consider implementing automated alerts for disk space utilization patterns that could indicate exploitation of this vulnerability, as the attack can occur gradually without immediate user awareness.