CVE-2012-3523 in INN
Summary
by MITRE
The STARTTLS implementation in nnrpd in INN before 2.5.3 does not properly restrict I/O buffering, which allows man-in-the-middle attackers to insert commands into encrypted 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 • 12/31/2024
The vulnerability described in CVE-2012-3523 affects the Network News Transfer Protocol daemon known as nnrpd within the INN (InterNetNews) software suite. This flaw exists in versions prior to 2.5.3 and represents a significant security weakness in the implementation of the STARTTLS functionality. The issue arises from improper handling of input/output buffering mechanisms during the secure connection establishment process, creating a window of opportunity for attackers to exploit the communication channel. The vulnerability specifically targets the transition period between plaintext and encrypted communication, where the system fails to adequately sanitize or validate incoming data streams.
The technical implementation flaw stems from the way nnrpd manages I/O operations during the STARTTLS handshake process. When a client initiates a connection and the server begins the TLS negotiation, the system should ensure that all incoming data is properly processed within the encrypted context. However, the vulnerability allows an attacker to inject cleartext commands that are subsequently processed after the TLS encryption is fully established. This creates a race condition where commands sent before the encryption is complete can be buffered and then executed in the context of the secure session, effectively bypassing the intended security protections. The flaw operates under the principle of command injection, where malicious input is executed in the context of the application process.
This vulnerability has significant operational impact as it enables man-in-the-middle attackers to perform command injection attacks against news servers that implement the affected nnrpd service. The attack vector allows adversaries to execute arbitrary commands within the context of the news server, potentially leading to unauthorized access to news articles, user data, or even complete system compromise. The similar nature to CVE-2011-0411 indicates a pattern of weaknesses in how STARTTLS implementations handle buffered data during secure connection establishment, suggesting that this may be a systemic issue rather than an isolated incident. The attack requires the adversary to be positioned between the client and server during the connection process, typically through network interception techniques such as ARP spoofing or DNS poisoning.
The security implications extend beyond simple command injection, as this vulnerability could enable attackers to manipulate news server configurations, access restricted newsgroups, or even use the compromised server as a launching point for further attacks. The vulnerability aligns with CWE-20, which describes improper input validation, and represents a specific case of CWE-94, which covers execution of arbitrary code. From an ATT&CK framework perspective, this vulnerability maps to techniques involving command and script injection, potentially enabling privilege escalation and lateral movement within network environments where news servers are deployed. The affected systems are particularly vulnerable in environments where news servers handle sensitive information or serve as part of larger network infrastructure components.
Mitigation strategies should focus on upgrading to INN version 2.5.3 or later, which contains the necessary fixes for the I/O buffering implementation. System administrators should also implement additional network security measures such as proper certificate validation, network segmentation, and monitoring for unusual command patterns in news server logs. The fix typically involves ensuring that all buffered data is properly validated and sanitized before being processed in the encrypted context, preventing the injection of cleartext commands that could be executed after TLS establishment. Organizations should also consider implementing network access controls and intrusion detection systems to monitor for potential exploitation attempts targeting this specific vulnerability.