CVE-2002-0285 in Outlook Express
Summary
by MITRE
Outlook Express 5.5 and 6.0 on Windows treats a carriage return ("CR") in a message header as if it were a valid carriage return/line feed combination (CR/LF), which could allow remote attackers to bypass virus protection and or other filtering mechanisms via a mail message with headers that only contain the CR, which causes Outlook to create separate headers.
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Analysis
by VulDB Data Team • 05/16/2019
This vulnerability in Microsoft Outlook Express 5.5 and 6.0 represents a significant protocol parsing flaw that exploits improper handling of line termination sequences in email headers. The issue stems from the application's failure to properly validate and process carriage return characters within message headers, treating a solitary carriage return as equivalent to a carriage return line feed combination. This behavior creates a parsing inconsistency that can be exploited by malicious actors to manipulate email processing mechanisms.
The technical flaw manifests when Outlook Express encounters a message header containing only a carriage return character without the accompanying line feed. Normally, email protocols such as smtp and mime require proper line termination sequences to delineate header fields and separate message components. However, Outlook Express 5.5 and 6.0 incorrectly process this single carriage return character, causing the application to interpret it as a complete line termination sequence. This misinterpretation results in the creation of separate, potentially malformed header fields that can bypass standard security filtering mechanisms designed to detect and block malicious content.
The operational impact of this vulnerability extends beyond simple message parsing errors, creating opportunities for attackers to circumvent security controls that rely on header validation. Attackers can craft malicious email messages where carefully placed carriage return characters in headers can cause Outlook Express to split headers in unexpected ways, potentially allowing virus scanning systems to miss malicious content or bypass spam filtering rules. This vulnerability particularly affects organizations relying on Outlook Express for email processing, as it undermines the integrity of security mechanisms designed to protect against email-based threats.
Security researchers have classified this issue under CWE-129 Input Validation and Representation, specifically addressing improper handling of line termination sequences in text processing. The vulnerability aligns with ATT&CK technique T1192 Spearphishing Attachment, where attackers can use malformed email headers to bypass security controls. Organizations using these vulnerable versions of Outlook Express face significant risk from email-based attacks that exploit this parsing inconsistency to deliver malicious payloads.
Mitigation strategies should prioritize immediate patching of affected systems, as Microsoft released security updates addressing this vulnerability. Network administrators should implement additional email filtering layers that validate header structures independently of client applications, ensuring that malformed headers are detected and quarantined before reaching end-user mailboxes. Organizations should also consider implementing email security appliances that can detect and block suspicious header manipulation patterns. Regular security assessments of email processing systems should include validation of line termination handling, and system administrators should monitor for unusual header processing behaviors that might indicate exploitation attempts.