CVE-2012-2200 in Sendmail
Summary
by MITRE
The default configuration of sendmail in IBM AIX 6.1 and 7.1, and VIOS 2.2.1.4-FP-25 SP-02, allows local users to gain privileges by entering a command in a .forward file in a home directory.
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Analysis
by VulDB Data Team • 01/02/2025
The vulnerability identified as CVE-2012-2200 represents a critical privilege escalation flaw in the default sendmail configuration across multiple IBM AIX and VIOS versions. This issue stems from the improper handling of .forward files, which are commonly used by sendmail to redirect email messages to alternative destinations. When a local user places a malicious command within a .forward file located in their home directory, the system executes this command with elevated privileges, effectively allowing unauthorized privilege escalation. The vulnerability specifically affects IBM AIX 6.1 and 7.1 operating systems along with VIOS 2.2.1.4-FP-25 SP-02, making it a widespread concern for organizations utilizing these platforms. The root cause of this vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, and CWE-78, which addresses OS command injection vulnerabilities. From an operational perspective, this vulnerability presents a significant risk as it requires minimal privileges for exploitation and can be leveraged by any local user to execute arbitrary commands with higher privileges. The attack vector is particularly concerning because it exploits the legitimate functionality of sendmail's .forward file mechanism, making detection more challenging. The default configuration of sendmail on these systems fails to properly sanitize or validate the contents of .forward files, creating an environment where user-controlled input can be executed as system commands. This vulnerability directly maps to ATT&CK technique T1068, which covers privilege escalation through the exploitation of system configuration weaknesses. The impact extends beyond simple command execution as it can enable attackers to establish persistent access, escalate privileges further, or extract sensitive system information. Organizations running affected systems face potential unauthorized access to critical system resources, data breaches, and the possibility of full system compromise. The vulnerability's exploitation does not require network access or specialized tools, making it particularly dangerous in environments where local user access is not properly restricted. The default sendmail configuration on these IBM systems creates an implicit trust relationship that should not exist, as it allows any local user to manipulate system behavior through simple file creation. This flaw demonstrates a fundamental security misconfiguration that violates the principle of least privilege and can be exploited to gain unauthorized access to system resources.
The technical implementation of this vulnerability relies on the specific way sendmail processes .forward files in the affected IBM AIX and VIOS environments. When a user's mail is processed by sendmail and the system encounters a .forward file in the user's home directory, the system executes the contents of this file as shell commands without proper validation or privilege separation. This behavior creates a dangerous execution context where user input directly translates to system command execution. The vulnerability is particularly insidious because it leverages legitimate system functionality rather than introducing new attack vectors, making it harder to detect through standard security monitoring. The .forward file mechanism was designed for legitimate email redirection purposes, but the implementation fails to properly isolate user input from system execution contexts. This issue is exacerbated by the fact that many system administrators may not be aware of the security implications of .forward file usage, especially in default configurations. The vulnerability exists at the intersection of file system permissions, mail system processing, and privilege management, creating a complex attack surface that can be exploited by users with minimal system access. From a security architecture standpoint, this vulnerability demonstrates the importance of proper input validation and privilege separation in system components. The default configuration of sendmail on these platforms fails to implement proper sandboxing or privilege reduction when processing user-controlled files, allowing for direct command execution with elevated privileges.
Mitigation strategies for CVE-2012-2200 require immediate action from system administrators to address the underlying configuration issues. The most effective immediate solution involves disabling or restricting the use of .forward files in the sendmail configuration, which can be accomplished through proper sendmail configuration parameters that prevent command execution in forward files. Organizations should implement strict file permission controls on home directories to prevent unauthorized modification of .forward files, ensuring that only authorized users can modify these system-critical files. The recommended approach includes disabling the .forward file functionality entirely or implementing strict validation mechanisms that prevent the execution of potentially malicious commands. System administrators should also consider implementing additional monitoring and alerting mechanisms to detect unauthorized modifications to .forward files or suspicious command execution patterns. Regular security audits should verify that sendmail configurations do not allow command execution in user-controlled files, and automated scanning tools can help identify systems with vulnerable configurations. The implementation of principle of least privilege should be enforced, ensuring that local users have minimal necessary permissions to prevent exploitation of this vulnerability. Organizations should also consider implementing file integrity monitoring solutions that can detect unauthorized changes to critical system files including .forward files. Patch management programs should be prioritized to address the underlying vulnerabilities in the IBM AIX and VIOS versions, with immediate updates to the affected systems. Network segmentation and access controls should be implemented to limit local user access to systems where this vulnerability exists, reducing the attack surface for potential exploitation. The vulnerability also highlights the importance of regular security assessments and configuration reviews to identify and remediate similar issues in other system components. Proper system hardening practices should be implemented to ensure that default configurations do not introduce unnecessary security risks, particularly in enterprise environments where multiple systems may be vulnerable to similar issues.