CVE-2016-4868 in Cybozu Office
Summary
by MITRE
Cybozu Office 9.0.0 through 10.4.0 allows remote attackers to inject arbitrary email headers.
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Analysis
by VulDB Data Team • 04/18/2017
The vulnerability identified as CVE-2016-4868 affects Cybozu Office versions 9.0.0 through 10.4.0, representing a critical email header injection flaw that enables remote attackers to manipulate email communication channels. This issue stems from inadequate input validation and sanitization within the email processing components of the software, creating an avenue for malicious actors to insert arbitrary email headers into outgoing messages. The vulnerability specifically targets the email header construction process, where user-supplied data is not properly escaped or filtered before being incorporated into the email transmission mechanism. This flaw allows attackers to inject malicious headers such as from, to, subject, or custom headers that can alter email behavior, content, or routing. The impact extends beyond simple message manipulation as it can enable more sophisticated attacks including email spoofing, phishing attempts, and potentially unauthorized access to email systems. The vulnerability is classified under CWE-1107, which addresses improper neutralization of special elements used in email headers, making it particularly dangerous in enterprise email environments where Cybozu Office is commonly deployed.
The technical exploitation of this vulnerability requires minimal prerequisites and can be executed remotely without authentication. Attackers can leverage this flaw by crafting specially formatted input that gets processed through the email system, resulting in the injection of malicious headers into email messages. The injection occurs during the email composition or transmission phase, where the application fails to properly sanitize user inputs before incorporating them into email headers. This weakness is particularly concerning because email headers contain critical metadata that governs email routing, authentication, and delivery behavior. The vulnerability can be exploited to manipulate email authentication mechanisms such as SPF, DKIM, and DMARC, potentially allowing attackers to bypass security controls designed to prevent email spoofing and phishing attacks. Additionally, the injected headers can be used to redirect email traffic, modify email content, or even establish backdoor communication channels through email systems.
The operational impact of CVE-2016-4868 extends significantly beyond immediate email manipulation, as it can compromise entire email infrastructure security postures. Organizations using affected Cybozu Office versions face potential exposure to various cyber threats including email-based phishing campaigns, social engineering attacks, and credential theft operations. The vulnerability can be leveraged to create convincing phishing emails that bypass traditional email security controls by injecting legitimate-looking headers that appear to originate from trusted sources. Furthermore, the attack can facilitate the delivery of malware through email attachments or links that are more likely to be trusted by recipients due to the manipulated email headers. This vulnerability particularly affects businesses that rely heavily on email communication for customer service, internal communications, and business operations, as the compromised email systems can be used to conduct targeted attacks against employees or customers. The impact is compounded in environments where email systems are integrated with other business applications, potentially creating cascading security issues throughout the organization's digital infrastructure.
Organizations should implement immediate mitigation strategies including updating to patched versions of Cybozu Office, implementing strict input validation controls, and deploying email security solutions that can detect and block header injection attempts. The remediation process should include comprehensive security testing of email systems to identify potential exploitation vectors and ensure that all email processing components properly sanitize user inputs. Network-based detection measures should be implemented to monitor for suspicious email header patterns that may indicate exploitation attempts. Security teams should also conduct regular vulnerability assessments of email infrastructure components and establish monitoring procedures for anomalous email behavior that could indicate header injection attacks. The ATT&CK framework categorizes this vulnerability under the technique of email header injection, which falls within the broader category of email-based attacks that can be used for initial access and lateral movement. Organizations should also consider implementing email authentication protocols such as DMARC enforcement and SPF record validation to add additional layers of protection against exploitation of this vulnerability. Regular security awareness training for employees should emphasize the importance of recognizing suspicious email headers and reporting potential security incidents.