CVE-2018-9846 in RoundCube
Summary
by MITRE
In Roundcube from versions 1.2.0 to 1.3.5, with the archive plugin enabled and configured, it's possible to exploit the unsanitized, user-controlled "_uid" parameter (in an archive.php _task=mail&_mbox=INBOX&_action=plugin.move2archive request) to perform an MX (IMAP) injection attack by placing an IMAP command after a %0d%0a sequence. NOTE: this is less easily exploitable in 1.3.4 and later because of a Same Origin Policy protection mechanism.
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Analysis
by VulDB Data Team • 02/27/2023
The vulnerability identified as CVE-2018-9846 affects Roundcube webmail applications in versions 1.2.0 through 1.3.5, specifically when the archive plugin is enabled and configured. This represents a critical security flaw that allows attackers to manipulate IMAP commands through improper input validation, creating potential for unauthorized access and data manipulation within the email system. The vulnerability stems from insufficient sanitization of user-controlled parameters, particularly the "_uid" parameter that is processed during archive operations.
The technical implementation of this vulnerability occurs within the archive.php script where the application processes requests with parameters including _task=mail, _mbox=INBOX, and _action=plugin.move2archive. The flaw manifests when the "_uid" parameter is not properly sanitized before being used in IMAP operations, allowing attackers to inject malicious IMAP commands. The exploitation technique involves appending a %0d%0a sequence followed by malicious IMAP commands, which leverages the underlying IMAP protocol's command structure to execute unauthorized operations on the mail server. This type of injection attack falls under CWE-94, representing an improper control of generation of code, specifically an IMAP injection vulnerability that bypasses normal input validation mechanisms.
The operational impact of this vulnerability extends beyond simple data theft, as successful exploitation could enable attackers to access, modify, or delete email messages stored on the IMAP server. Attackers could potentially move messages between folders, delete archived emails, or even access other users' mailboxes if proper access controls are not in place. The vulnerability is particularly concerning because it operates at the protocol level, meaning that successful exploitation could undermine the fundamental security assumptions of the email system and potentially allow for broader compromise of the mail infrastructure. The Same Origin Policy protection introduced in version 1.3.4 significantly reduces the attack surface, but the vulnerability remains exploitable in earlier versions and could be combined with other attacks to achieve more severe outcomes.
Organizations using affected Roundcube versions should prioritize immediate patching to address this vulnerability, as the attack vector is relatively straightforward to exploit and could lead to significant data compromise. The mitigation strategy should include not only updating to patched versions but also implementing additional network-level protections such as firewall rules that restrict access to sensitive IMAP operations and monitoring for unusual IMAP command patterns. Security teams should also consider implementing web application firewalls to detect and block malicious %0d%0a sequences in request parameters, and conduct thorough security testing of all webmail applications to identify similar input validation flaws. The vulnerability demonstrates the importance of proper input sanitization in web applications that interact with backend protocols, and aligns with ATT&CK technique T1071.004 for application layer protocol manipulation.