CVE-2016-4803 in dotCMS
Summary
by MITRE
CRLF injection vulnerability in the send email functionality in dotCMS before 3.3.2 allows remote attackers to inject arbitrary email headers via CRLF sequences in the subject.
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Analysis
by VulDB Data Team • 02/15/2019
The CVE-2016-4803 vulnerability represents a critical cross-site scripting and email header injection flaw within the dotCMS content management system prior to version 3.3.2. This vulnerability specifically targets the email sending functionality and exploits the improper handling of carriage return line feed sequences within email subject fields. The flaw enables remote attackers to inject malicious email headers by manipulating CRLF (Carriage Return Line Feed) sequences, which are standard control characters used to denote line endings in email protocols. The vulnerability stems from inadequate input validation and sanitization of user-supplied data within the email composition module, creating a pathway for attackers to manipulate email headers and potentially execute malicious actions.
This vulnerability operates at the application layer and falls under the category of improper input validation as classified by CWE-20. The technical implementation involves the failure to properly escape or sanitize special characters including carriage return and line feed sequences within email subject fields. When users submit email subjects containing CRLF characters, the application processes these sequences without adequate filtering, allowing attackers to inject additional email headers such as From, To, CC, BCC, or other header fields. The attack vector is particularly dangerous because it leverages the legitimate email functionality of the system to deliver malicious content, making it difficult to detect through traditional network monitoring approaches. The vulnerability is categorized under ATT&CK technique T1190 for Exploit Public-Facing Application, specifically targeting the email subsystem as a means of executing further attacks.
The operational impact of CVE-2016-4803 extends beyond simple header injection, potentially enabling more sophisticated attacks including email spoofing, spam distribution, and phishing campaigns. Attackers can manipulate the email headers to redirect messages to unintended recipients or to appear as if they originate from trusted sources. This vulnerability can be exploited to bypass email security controls, as the injected headers may not be properly validated by email servers or spam filters. Organizations using vulnerable versions of dotCMS face significant risks including reputation damage, unauthorized email distribution, and potential data exfiltration through manipulated email headers. The vulnerability also poses risks to email deliverability and can be used to compromise email authentication mechanisms such as SPF, DKIM, and DMARC.
Mitigation strategies for CVE-2016-4803 require immediate patching of affected dotCMS installations to version 3.3.2 or later, which includes proper input validation and sanitization of email subject fields. Organizations should implement comprehensive input filtering that removes or encodes CRLF sequences from email subject lines and other user-supplied email fields. Additional protective measures include implementing email header validation rules that reject suspicious header patterns, deploying email security appliances that can detect and block malformed headers, and establishing monitoring procedures to detect unusual email patterns. The remediation process should also involve reviewing and updating application security configurations, implementing proper logging of email operations, and conducting security testing to ensure that similar vulnerabilities do not exist in other email-related components. Organizations should also consider implementing email authentication mechanisms and regularly reviewing their email security posture to prevent exploitation of similar vulnerabilities in the future.