CVE-2010-1132 in SpamAssassin Milter Plugin
Summary
by MITRE
The mlfi_envrcpt function in spamass-milter.cpp in SpamAssassin Milter Plugin 0.3.1, when using the expand option, allows remote attackers to execute arbitrary system commands via shell metacharacters in the RCPT TO field of an email message.
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Analysis
by VulDB Data Team • 05/03/2026
The vulnerability identified as CVE-2010-1132 represents a critical command injection flaw within the SpamAssassin Milter Plugin version 0.3.1, specifically affecting the mlfi_envrcpt function in the spamass-milter.cpp component. This vulnerability arises from insufficient input validation and sanitization when processing email recipient addresses through the RCPT TO field during the SMTP transaction process. The issue manifests when the milter plugin utilizes the expand option, which enables dynamic expansion of recipient addresses, creating an attack surface where malicious actors can inject shell metacharacters that get interpreted and executed by the underlying system shell.
The technical exploitation of this vulnerability occurs during the email delivery process when an attacker crafts a malicious email message containing specially formatted RCPT TO field data. When the spamass-milter plugin processes this field with the expand option enabled, it fails to properly sanitize the input before passing it to shell execution functions. This allows attackers to inject shell commands that are subsequently executed with the privileges of the milter process, typically running as a system user with elevated permissions. The vulnerability directly maps to CWE-78, which describes improper neutralization of special elements used in OS commands, and represents a classic command injection attack vector that can be leveraged for arbitrary code execution.
The operational impact of this vulnerability is severe and far-reaching, as it provides remote attackers with the capability to execute arbitrary system commands on the affected server. Attackers can potentially escalate privileges, gain persistent access, exfiltrate sensitive data, or use the compromised system as a launch point for further attacks within the network infrastructure. The milter plugin typically runs in a privileged context, making successful exploitation particularly dangerous as it can lead to complete system compromise. This vulnerability aligns with ATT&CK technique T1059.001, which covers command and scripting interpreter, and represents a critical entry point for attackers seeking to establish persistent access or escalate privileges within the email infrastructure.
Mitigation strategies for CVE-2010-1132 should begin with immediate patching of the SpamAssassin Milter Plugin to version 0.3.2 or later, which contains the necessary input sanitization fixes. Organizations should also implement network-level restrictions to limit access to the milter service, disable the expand option if not strictly required, and employ proper input validation at multiple layers of the email processing pipeline. Additionally, monitoring for unusual command execution patterns and implementing robust logging of milter activities can help detect exploitation attempts. Security teams should also consider implementing network segmentation and privilege separation to limit the potential impact of successful exploitation, ensuring that even if the milter process is compromised, the attacker's access remains restricted to prevent further lateral movement within the network infrastructure.