CVE-2011-1432 in SCOoffice Server
Summary
by MITRE
The STARTTLS implementation in SCO SCOoffice Server 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-2011-1432 represents a critical flaw in the STARTTLS implementation of SCO SCOoffice Server that fundamentally undermines the security of encrypted email communications. This issue arises from improper handling of input/output buffering during the transition from plaintext to encrypted SMTP sessions, creating a window of opportunity for attackers to exploit the communication channel. The vulnerability specifically affects the server's ability to properly manage data flow between cleartext and encrypted states, allowing malicious actors to inject commands that will be processed after the TLS encryption is established. This flaw directly relates to the broader category of command injection attacks that have plagued various email server implementations over the years, with the specific characteristics that distinguish it from similar vulnerabilities such as CVE-2011-0411.
The technical implementation flaw stems from inadequate buffering mechanisms that fail to properly isolate or sanitize data streams during the cryptographic handshake process. When an SMTP client initiates a connection to the SCOoffice Server, the system should maintain strict separation between cleartext commands sent before TLS establishment and encrypted commands that follow. However, the flawed implementation allows data to remain in buffers or queues where it can be processed in an unintended order. This creates a scenario where an attacker can send a cleartext command that appears to be processed immediately, but due to the buffering issue, the command gets executed after the TLS session has been established, effectively bypassing the encryption layer. The vulnerability operates at the protocol level, specifically targeting the SMTP transaction process where STARTTLS is negotiated, making it particularly dangerous for email server environments that rely on proper encryption to protect sensitive communications.
The operational impact of this vulnerability extends beyond simple command injection, as it fundamentally compromises the integrity and confidentiality of email communications within the SCOoffice Server environment. An attacker exploiting this vulnerability can potentially execute arbitrary commands on the server, gain unauthorized access to email accounts, or even escalate privileges within the system. The man-in-the-middle attack vector allows adversaries to manipulate email content, redirect messages, or intercept sensitive information without detection, as the malicious commands appear to originate from legitimate sources within the encrypted session. This vulnerability particularly affects organizations that rely on SCOoffice Server for email services, as it undermines the trust model that encryption is supposed to provide, making it possible for attackers to compromise the entire email infrastructure. The attack can be executed remotely without requiring authentication, making it particularly dangerous for systems that are exposed to the internet.
Security mitigations for CVE-2011-1432 should focus on implementing proper input validation and buffering mechanisms that prevent data from being processed out of sequence during the TLS transition. Organizations should ensure that all data streams are properly sanitized and isolated during the cryptographic handshake process, with strict enforcement of command ordering and execution sequences. The recommended approach includes implementing robust buffer management techniques that prevent data from remaining in intermediate states where it could be processed after encryption is established. Additionally, system administrators should consider disabling STARTTLS functionality if it cannot be properly secured, or implementing additional network-level protections such as firewall rules that restrict access to the affected SMTP ports. From a compliance perspective, this vulnerability aligns with CWE-20 Improper Input Validation and CWE-312 Cleartext Storage of Sensitive Information, while the attack methodology maps to ATT&CK technique T1071.004 Application Layer Protocol: Email Protocols, highlighting the need for comprehensive network security controls. Organizations should also implement network monitoring to detect unusual command patterns that might indicate exploitation attempts, and regularly audit their email server configurations to ensure proper handling of encrypted communications.