CVE-2002-1777 in Norton Antivirus
Summary
by MITRE
** DISPUTED ** NOTE: this issue has been disputed by the vendor. Symantec Norton AntiVirus (NAV) 2002 allows remote attackers to bypass e-mail scanning via a filename in the Content-Type field with an excluded extension such as .nch or .dbx, but a malicious extension in the Content-Disposition field, which is used by Outlook to obtain the file name. NOTE: the vendor has disputed this issue, acknowledging that the initial scan is bypassed, but Norton AntiVirus or the Office plug-in would detect the virus before it is executed.
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Analysis
by VulDB Data Team • 09/01/2025
This vulnerability resides within Symantec Norton AntiVirus 2002's email scanning mechanism, representing a sophisticated bypass attack that exploits the differing file extension handling between email headers. The flaw specifically targets the Content-Type and Content-Disposition fields within email messages, where the Content-Type field contains an excluded extension such as .nch or .dbx while the Content-Disposition field carries a malicious extension. This discrepancy creates a window of opportunity for attackers to circumvent initial email scanning by leveraging the fact that NAV performs initial filtering based on Content-Type field extensions, which are often whitelisted for certain file types. The vulnerability demonstrates a fundamental misalignment in how email clients and security solutions interpret file naming conventions, particularly when Outlook's Content-Disposition field is used to determine actual file names for attachment handling.
The technical implementation of this vulnerability relies on the email parsing behavior of both the email client and the antivirus solution. When Norton AntiVirus processes incoming email, it initially examines the Content-Type header field to determine whether to scan the attachment, using the extension found there as the primary indicator. However, the Content-Disposition field, which Outlook uses to specify the filename for saving attachments, contains the actual malicious extension that would trigger detection if properly scanned. This creates a race condition where the initial scan is bypassed due to the excluded extension in Content-Type, while the malicious extension in Content-Disposition remains undetected until later processing stages. The vulnerability is classified as a weakness in input validation and security policy enforcement, aligning with CWE-20, which covers improper input validation in software systems.
The operational impact of this vulnerability extends beyond simple bypass of email scanning, potentially allowing attackers to deliver malware payloads that would otherwise be blocked by standard antivirus measures. This represents a significant risk in corporate environments where email filtering is a primary defense mechanism against malware distribution. The bypass occurs during the initial email processing phase, meaning that malicious code could be delivered to users' systems without immediate detection, potentially leading to successful phishing attacks, credential theft, or system compromise. The vulnerability particularly affects organizations that rely heavily on email security as their primary line of defense, creating a false sense of security when the antivirus solution appears to be functioning correctly but is actually allowing malicious attachments through the scanning gap.
Security professionals should consider this vulnerability in the context of broader email security frameworks and attack patterns documented in MITRE ATT&CK matrix, specifically related to email-based attacks and evasion techniques. The attack vector aligns with techniques used in social engineering campaigns where attackers manipulate email headers to bypass security controls. Organizations should implement layered security approaches that include multiple detection points beyond initial email scanning, such as sandboxing for suspicious attachments, network-based intrusion detection systems, and user education programs. Additionally, the vendor's acknowledgment of the initial bypass while noting detection by other components suggests that a comprehensive security strategy must account for multiple detection points rather than relying on a single protective layer. This vulnerability underscores the importance of proper email header validation and the need for security solutions to maintain consistent detection policies across all email processing stages.
The disputed nature of this vulnerability by the vendor highlights the complexity of email security analysis and the challenges in defining clear boundaries for detection capabilities. While the vendor acknowledges the initial bypass, their assertion that the Office plug-in detects the virus before execution suggests that the vulnerability may be less severe than initially described. However, the time window between initial bypass and later detection provides sufficient opportunity for attackers to execute their payloads, particularly in environments where multiple layers of protection are not implemented. This case study emphasizes the need for continuous security validation and the importance of understanding how different security components interact within complex email processing environments. Organizations should conduct regular vulnerability assessments that consider both the specific mechanisms described in CVEs and the broader operational context in which these vulnerabilities might be exploited.