Source: cve@mitre.org
Command execution via shell metachars in INN daemon (innd) 1.5 using "newgroup" and "rmgroup" control messages, and others.
Critical vulnerability in INN (InterNetNews) daemon (innd) versions 1.5 allows for remote command execution. Attackers can inject malicious commands through specially crafted control messages, potentially gaining full control of the vulnerable server and compromising sensitive data.
Step 1: Target Identification: The attacker identifies a server running a vulnerable version of the INN daemon (innd) 1.5.
Step 2: Payload Crafting: The attacker crafts a malicious control message, such as newgroup or rmgroup, containing shell metacharacters and a payload (e.g., a command to download and execute a reverse shell, or to create a new user).
Step 3: Message Delivery: The attacker sends the crafted control message to the INN daemon, typically via a network connection (e.g., TCP port 119 for NNTP).
Step 4: Command Injection: The INN daemon processes the control message. Due to the lack of input validation, the shell metacharacters in the message are interpreted by the shell, leading to command execution.
Step 5: Payload Execution: The injected shell commands are executed with the privileges of the innd user.
Step 6: System Compromise: The attacker gains control of the system, potentially leading to data exfiltration, further privilege escalation, or denial of service.
The vulnerability stems from insufficient input validation and sanitization of user-supplied data within the INN daemon's control message handling. Specifically, the newgroup and rmgroup control messages, and potentially others, fail to properly escape or filter shell metacharacters (e.g., ;, |, &, $ ) within the group name or other parameters. This allows an attacker to inject arbitrary shell commands. When the daemon processes these messages, the injected commands are executed with the privileges of the innd user, which often has elevated access to newsgroup data and system resources. The root cause is a lack of secure coding practices, specifically a failure to implement proper input validation and output encoding to prevent command injection.
Due to the age of the vulnerability, it's likely that various threat actors, including script kiddies and potentially more sophisticated actors, could exploit this. While specific APT attribution is difficult, any actor seeking to compromise a system running a vulnerable INN daemon could utilize this. This vulnerability is not specifically listed in the CISA KEV database, but the underlying principle of command injection makes it relevant to the broader threat landscape.
Network traffic analysis: Examine network traffic for suspicious NNTP control messages containing shell metacharacters (e.g., ;, |, &, $ ) in the newgroup, rmgroup, or other control message parameters.
Log analysis: Review INN daemon logs for unusual activity, such as unexpected command executions or errors related to control message processing. Look for evidence of shell command execution within the logs.
File system monitoring: Monitor the file system for the creation of new files or modifications to existing files that could indicate malicious activity, such as the download and execution of a reverse shell.
Intrusion Detection Systems (IDS): Deploy and configure an IDS to detect malicious NNTP control messages containing shell metacharacters. Create custom signatures or rules to identify exploit attempts.
Host-based Intrusion Detection Systems (HIDS): Monitor system logs and file integrity to detect any unauthorized changes or suspicious activities.
Upgrade: Upgrade to a patched version of INN or a more modern news server software that addresses this vulnerability. If upgrading is not possible, apply the vendor's recommended patches.
Input Validation: Implement robust input validation and sanitization for all control message parameters. Ensure that shell metacharacters are properly escaped or filtered to prevent command injection.
Least Privilege: Run the INN daemon with the least privileges necessary. Avoid running the daemon as root or with excessive permissions.
Network Segmentation: Segment the network to limit the impact of a successful exploit. Restrict network access to the INN server to only necessary hosts.
Intrusion Detection and Prevention Systems (IDPS): Deploy and configure an IDPS to detect and block malicious NNTP control messages.
Regular Security Audits: Conduct regular security audits and penetration testing to identify and address vulnerabilities.