CVE-2005-0493 in Biz Mail Form
Summary
by MITRE
CRLF injection vulnerability in bizmail.cgi in Biz Mail Form before 2.2 allows remote attackers to bypass the email check and send spam e-mail via CRLF sequences and forged mail headers in the email parameter.
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Analysis
by VulDB Data Team • 06/06/2019
The CVE-2005-0493 vulnerability represents a critical cross-site scripting and email header injection flaw in the Biz Mail Form application's bizmail.cgi script. This vulnerability stems from inadequate input validation and sanitization of user-supplied email parameters, specifically targeting the email field that processes user input through the email parameter. The flaw enables attackers to inject carriage return line feed sequences into email headers, allowing manipulation of the email sending process. This vulnerability falls under the CWE-113 category for Improper Neutralization of CRLF Sequences in HTTP Headers, which is a well-documented weakness in web application security. The vulnerability exists within the application's email processing logic where user input is directly incorporated into email headers without proper sanitization.
The technical exploitation of this vulnerability occurs when an attacker crafts malicious input containing CRLF sequences such as \r\n or %0D%0A within the email parameter field. These sequences allow the attacker to insert forged email headers into the message being sent, effectively bypassing the email validation checks that the application normally performs. The injected headers can manipulate the From, To, Subject, or other email headers, enabling the attacker to send spam emails that appear to originate from legitimate sources. The vulnerability is particularly dangerous because it allows attackers to forge email headers and potentially bypass spam filters that rely on header validation. This type of attack aligns with ATT&CK technique T1566.001 for Phishing through Social Engineering, where attackers manipulate email headers to appear more legitimate and avoid detection.
The operational impact of this vulnerability extends beyond simple spamming activities, as it provides attackers with a mechanism to conduct various malicious email-based attacks. The bypass of email validation checks means that spammers can use the vulnerable application as a relay for sending unsolicited emails, potentially leading to the application being blacklisted by email providers. The vulnerability also poses risks to the organization's reputation and can be exploited for phishing campaigns where forged email headers make messages appear more credible to recipients. Attackers can leverage this vulnerability to send large volumes of spam emails, potentially causing the application to be flagged by email security systems and resulting in service disruption. The vulnerability's exploitation can also facilitate other attack vectors such as email-based social engineering campaigns or even serve as a stepping stone for more sophisticated attacks.
Mitigation strategies for CVE-2005-0493 should focus on implementing proper input validation and sanitization of user-supplied email parameters. The most effective approach involves removing or encoding CRLF sequences from email input fields before processing, ensuring that any user-supplied email addresses are properly validated against standard email format specifications. Organizations should implement strict input filtering that rejects or sanitizes any input containing control characters that could be used for header injection. The fix should include proper header encoding techniques such as using standard email libraries that automatically handle header sanitization, implementing proper email validation routines, and ensuring that all user input is properly escaped before being used in email headers. Additionally, network-level security controls such as email filtering and monitoring should be implemented to detect and prevent abuse of vulnerable applications. This vulnerability demonstrates the critical importance of input validation in web applications and aligns with security best practices outlined in the OWASP Top Ten and NIST cybersecurity guidelines for preventing injection attacks.