CVE-2002-2034 in Procmail Email Sanitizer
Summary
by MITRE
The Email Sanitizer before 1.133 for Procmail allows remote attackers to bypass the mail filter and execute arbitrary code via crafted recursive multipart MIME attachments.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 07/08/2024
The vulnerability identified as CVE-2002-2034 resides within the Email Sanitizer component of Procmail versions prior to 1.133, representing a critical security flaw that undermines email filtering mechanisms. This vulnerability specifically targets the processing of recursive multipart MIME attachments, which are email structures that contain nested email messages within other email messages. The flaw enables malicious actors to craft specially designed email attachments that can bypass the intended filtering behavior of the sanitizer, ultimately leading to arbitrary code execution on systems that process these emails. The vulnerability exploits a fundamental weakness in how the sanitizer handles nested MIME structures, creating a pathway for attackers to circumvent security controls designed to prevent malicious content from entering email systems.
The technical implementation of this vulnerability stems from improper handling of recursive MIME attachment structures within the Procmail Email Sanitizer. When the sanitizer encounters a multipart MIME message with nested attachments, it fails to properly validate or process the recursive nature of these structures. This processing error occurs at the level of MIME parsing and content evaluation, where the sanitizer does not adequately distinguish between legitimate nested email structures and maliciously crafted recursive attachments designed to exploit the parsing logic. The vulnerability manifests when the sanitizer attempts to process recursive multipart MIME constructs, allowing attackers to construct email messages where the recursive elements contain shell commands or executable code that gets executed during the sanitization process rather than being properly filtered out.
The operational impact of CVE-2002-2034 is severe and multifaceted, affecting organizations that rely on Procmail for email filtering and security. Systems running vulnerable versions of Procmail become susceptible to remote code execution attacks, potentially allowing attackers to gain unauthorized access to email servers and underlying systems. The vulnerability can be exploited by sending specially crafted emails to any user or system that processes mail through the vulnerable Procmail configuration, making it particularly dangerous in enterprise environments where email is a primary communication channel. Once exploited, the vulnerability could enable attackers to execute arbitrary commands on the affected system, potentially leading to complete system compromise, data exfiltration, or the establishment of persistent backdoors within the email infrastructure. The recursive nature of the vulnerability means that even sophisticated email security measures might be bypassed, as the attack vector exploits the fundamental parsing logic rather than surface-level filtering rules.
Mitigation strategies for CVE-2002-2034 primarily focus on upgrading to the patched version of Procmail, specifically version 1.133 or later, which addresses the recursive MIME processing flaw. Organizations should also implement additional defensive measures including strict MIME structure validation, implementing content filtering rules that reject suspicious recursive attachment patterns, and deploying intrusion detection systems to monitor for anomalous email processing behavior. Network-level protections such as email gateway filtering and sandboxing of suspicious email content can provide additional layers of defense. From a compliance perspective, this vulnerability aligns with CWE-129 and CWE-134 categories related to improper input validation and improper format string handling, respectively. The attack pattern follows typical techniques described in ATT&CK framework under T1190 for exploit public-facing application and T1059 for command and scripting interpreter, demonstrating how this vulnerability can be leveraged as a foothold for broader system compromise. Organizations should also consider implementing email security solutions that provide additional validation beyond what Procmail offers, particularly in environments where upgrading the core email processing software might not be immediately feasible.