CVE-2003-1330 in MAILsweeper
Summary
by MITRE
Clearswift MAILsweeper for SMTP 4.3.6 SP1 does not execute custom "on strip unsuccessful" hooks, which allows remote attackers to bypass e-mail attachment filtering policies via an attachment that MAILsweeper can detect but not remove.
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Analysis
by VulDB Data Team • 06/16/2018
The vulnerability identified as CVE-2003-1330 affects Clearswift MAILsweeper for SMTP version 4.3.6 SP1, representing a critical flaw in email security filtering mechanisms. This issue manifests within the email attachment filtering system where the software fails to properly execute custom hooks designed to handle situations when attachment stripping operations are unsuccessful. The vulnerability stems from a design flaw in how the system manages failed attachment removal attempts, creating a potential security gap that could be exploited by malicious actors. The flaw specifically impacts the software's ability to maintain consistent security policies when dealing with certain types of email attachments that can be detected by the system but cannot be completely removed due to implementation limitations.
The technical nature of this vulnerability places it within the domain of CWE-20, which describes "Improper Input Validation" and CWE-310, which addresses "Cryptographic Issues." The flaw occurs when MAILsweeper successfully detects malicious or unwanted attachments but encounters failures during the stripping process, leaving the attachment partially or completely in the email stream. This creates a scenario where the system's security policy enforcement is bypassed because the custom hooks that should be triggered when stripping operations fail are not executed. The underlying mechanism involves the software's hook execution framework failing to properly invoke user-defined scripts or procedures when the primary filtering operation cannot complete successfully, thereby allowing potentially harmful attachments to pass through the security controls.
The operational impact of this vulnerability extends beyond simple bypass of email filtering policies to potentially compromise entire email security infrastructures. Attackers can exploit this weakness by crafting email attachments that MAILsweeper can detect but cannot strip completely, effectively circumventing the intended security controls. This vulnerability represents a significant concern for organizations relying on MAILsweeper for email security, as it allows for the delivery of filtered content that should have been blocked. The attack vector is particularly dangerous because it requires minimal sophistication from the attacker, who only needs to ensure their malicious attachment triggers the detection mechanism while avoiding complete removal. This creates a persistent threat where malicious content can bypass security measures that are designed to prevent such attacks, potentially leading to data breaches, malware infections, or other security incidents that could affect the organization's email infrastructure and overall security posture.
Organizations affected by this vulnerability should implement immediate mitigations including updating to the latest version of MAILsweeper that addresses this specific flaw, as well as implementing additional email security controls such as spam filtering, content filtering, and email encryption. The ATT&CK framework categorizes this type of vulnerability under T1190 - "Exploit Public-Facing Application" and T1078 - "Valid Accounts," as attackers could potentially leverage this weakness to bypass email security controls and gain access to sensitive information. Network administrators should also consider implementing additional monitoring and logging of email traffic to detect potential exploitation attempts, while security teams should review their email security policies to ensure proper handling of edge cases in attachment filtering. The remediation process should include thorough testing of updated software configurations to ensure that hook execution mechanisms function properly and that all custom security policies are correctly enforced, preventing the bypass of email attachment filtering controls that could otherwise allow malicious content to reach end users.