CVE-2001-0713 in Sendmail
Summary
by MITRE
Sendmail before 8.12.1 does not properly drop privileges when the -C option is used to load custom configuration files, which allows local users to gain privileges via malformed arguments in the configuration file whose names contain characters with the high bit set, such as (1) macro names that are one character long, (2) a variable setting which is processed by the setoption function, or (3) a Modifiers setting which is processed by the getmodifiers function.
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Analysis
by VulDB Data Team • 10/04/2025
The vulnerability described in CVE-2001-0713 represents a critical privilege escalation flaw in sendmail versions prior to 8.12.1 that stems from improper privilege handling during configuration file processing. This issue specifically manifests when the sendmail daemon utilizes the -C command line option to load custom configuration files, creating a scenario where local attackers can exploit malformed arguments within these configuration files to elevate their privileges. The vulnerability operates through a combination of weak input validation and insufficient privilege management mechanisms that fail to properly sanitize or validate configuration file contents before processing them with elevated privileges.
The technical exploitation of this vulnerability relies on the manipulation of configuration file names containing characters with the high bit set, which creates a specific parsing condition within sendmail's configuration processing pipeline. This flaw affects three distinct processing paths within the sendmail codebase: macro name processing for single-character names, variable setting evaluation through the setoption function, and modifier configuration handling via the getmodifiers function. Each of these pathways represents a potential entry point for privilege escalation attacks where malformed input can cause sendmail to execute code with root privileges instead of dropping privileges as expected. The vulnerability is particularly dangerous because it leverages the legitimate configuration loading mechanism while exploiting the trust placed in configuration file contents, making detection and prevention challenging.
From an operational perspective, this vulnerability creates a significant security risk for systems running vulnerable sendmail versions, as local users with minimal privileges can potentially escalate to root access. The attack vector requires the attacker to have write access to configuration files or the ability to influence the configuration loading process, which is often achievable in shared hosting environments or systems where configuration files are managed by less privileged users. The impact extends beyond simple privilege escalation to potentially allow complete system compromise, as the attacker can leverage root privileges to modify system files, install backdoors, or exfiltrate sensitive data. This vulnerability directly relates to CWE-276, which addresses improper privileges, and aligns with ATT&CK technique T1068, privilege escalation through configuration file manipulation, making it a significant concern for enterprise security operations.
The exploitation of this vulnerability demonstrates the importance of proper input validation and privilege management in security-critical applications. The flaw highlights a fundamental design weakness in how sendmail handles configuration file processing, particularly when dealing with special character sets that may not be properly sanitized or validated. Organizations should implement immediate mitigations including upgrading to sendmail version 8.12.1 or later, which contains the necessary patches to address the privilege dropping mechanism. Additionally, system administrators should review and restrict write permissions on sendmail configuration files, implement file integrity monitoring solutions, and establish proper access controls to prevent unauthorized modification of configuration resources. The vulnerability serves as a reminder of the critical importance of privilege separation in daemon processes and the necessity of validating all inputs, especially those that can influence system behavior through configuration processing.