CVE-2004-0052 in MAILsweeper
Summary
by MITRE
Multiple content security gateway and antivirus products allow remote attackers to bypass content restrictions via MIME messages that use non-standard separator characters, or use standard separators incorrectly, within MIME headers, fields, parameters, or values, which may be interpreted differently by mail clients.
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Analysis
by VulDB Data Team • 06/21/2018
This vulnerability resides in content security gateways and antivirus products that process email traffic, specifically targeting the handling of MIME (Multipurpose Internet Mail Extensions) message structures. The flaw stems from improper parsing of MIME headers and parameters, where these security products fail to correctly interpret non-standard or incorrectly formatted MIME separators. When attackers craft malicious email messages using unconventional separator characters or misplace standard separators within MIME headers, fields, parameters, or values, the security appliances may misinterpret the message structure and incorrectly classify the content as safe, thereby allowing malicious payloads to bypass content restrictions. This vulnerability represents a classic example of improper input validation and parsing logic that affects email security systems.
The technical implementation of this vulnerability involves the manipulation of MIME message boundaries and field delimiters that are typically defined by standards such as RFC 2045 and RFC 2046. Standard MIME separators include semicolons for parameter delimiters, colons for header field separators, and specific boundary characters for multipart messages. When security appliances process these messages, they may not properly validate or normalize the separator characters, allowing attackers to exploit variations in how different mail clients interpret these characters. The vulnerability specifically targets the parsing logic of content security gateways, which are designed to inspect and filter email content based on predefined security policies, but fail to properly handle malformed or non-standard MIME structures.
The operational impact of this vulnerability is significant as it allows remote attackers to bypass content restrictions without requiring authentication or direct system access. Attackers can craft MIME messages that appear legitimate to security appliances but contain malicious content that is either hidden in non-standard locations or incorrectly interpreted due to the flawed parsing logic. This creates a scenario where security policies designed to prevent unauthorized content delivery or malicious attachments can be circumvented, potentially leading to data exfiltration, malware delivery, or other malicious activities. The vulnerability affects the fundamental security posture of organizations that rely on these content security gateways for email protection, as it undermines the core function of filtering and inspecting email traffic.
Organizations should implement comprehensive mitigations including updating security appliances to versions that properly handle MIME parsing, implementing additional content validation checks beyond standard security policies, and deploying multiple layers of email security controls. The vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and relates to ATT&CK technique T1192, which involves exploiting vulnerabilities in email security systems. Security teams should also consider implementing network segmentation, enhanced email header analysis, and regular security assessments of content filtering appliances to detect and prevent exploitation attempts. Additionally, organizations should ensure their security appliances are configured with strict MIME parsing rules and that regular firmware updates are applied to address known vulnerabilities in content security systems.