CVE-2011-1430 in IMail
Summary
by MITRE
The STARTTLS implementation in the server in Ipswitch IMail 11.03 and earlier does not properly restrict I/O buffering, which allows man-in-the-middle attackers to insert commands into encrypted SMTP sessions by sending a cleartext command that is processed after TLS is in place, related to a "plaintext command injection" attack, a similar issue to CVE-2011-0411.
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Analysis
by VulDB Data Team • 12/01/2024
The vulnerability identified as CVE-2011-1430 represents a critical security flaw in the Ipswitch IMail server's implementation of the STARTTLS protocol for email servers. This issue affects versions 11.03 and earlier, where the server's handling of input/output buffering during the TLS negotiation process creates a window of opportunity for attackers to exploit. The flaw specifically manifests in how the server processes command sequences during the transition from plaintext to encrypted communication, creating a scenario where malicious actors can inject commands into otherwise secure SMTP sessions.
The technical root cause of this vulnerability lies in the improper management of I/O buffering within the server's STARTTLS implementation. When a client initiates a TLS connection through the STARTTLS command, the server should ensure that all commands received during the handshake process are properly handled within the encrypted context. However, the flawed implementation allows for cleartext commands to be buffered and subsequently processed after the TLS encryption is established. This creates a race condition where an attacker can send a malicious command in cleartext before the TLS connection is fully secured, and then have that command executed once the encryption is in place, effectively bypassing the intended security protections.
From an operational perspective, this vulnerability enables man-in-the-middle attackers to perform command injection attacks against email servers that implement STARTTLS. The impact extends beyond simple data interception, as attackers can potentially execute arbitrary commands on the server, modify email content, redirect messages, or even gain unauthorized access to the mail server's functionality. The vulnerability is particularly concerning because it operates silently within the normal SMTP protocol flow, making detection difficult and allowing attackers to maintain persistence in the compromised environment. This issue is classified as a plaintext command injection attack, which aligns with the broader category of command injection vulnerabilities documented in CWE-77 and is related to the more general class of protocol-level attacks covered by ATT&CK technique T1071.004 for application layer protocol manipulation.
The security implications of this vulnerability are significant for organizations relying on Ipswitch IMail servers for email services. Attackers exploiting this flaw can potentially compromise the integrity and confidentiality of email communications, leading to data breaches, unauthorized access to email accounts, and potential lateral movement within networks. The vulnerability affects the fundamental security promise of TLS encryption, undermining the trust that users place in encrypted email communications. Organizations should implement immediate mitigations including upgrading to patched versions of Ipswitch IMail, implementing additional network monitoring to detect anomalous command sequences, and reviewing existing email security policies to address potential command injection vectors. The vulnerability also highlights the importance of proper input validation and buffering management in cryptographic protocol implementations, as outlined in security best practices from NIST SP 800-57 and ISO/IEC 27001 standards for secure system design and implementation.