CVE-2016-3403 in Zimbra Collaboration
Summary
by MITRE
Multiple cross-site request forgery (CSRF) vulnerabilities in the Admin Console in Zimbra Collaboration before 8.6.0 Patch 8 allow remote attackers to hijack the authentication of administrators for requests that (1) add, (2) modify, or (3) remove accounts by leveraging failure to use of a CSRF token and perform referer header checks, aka bugs 100885 and 100899.
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Analysis
by VulDB Data Team • 10/28/2022
The vulnerability described in CVE-2016-3403 represents a critical cross-site request forgery weakness affecting the Zimbra Collaboration Admin Console prior to version 8.6.0 Patch 8. This flaw resides within the administrative interface of the email server platform, creating a significant security risk for organizations relying on Zimbra for their communication infrastructure. The vulnerability stems from insufficient protection mechanisms that fail to properly validate user authentication tokens and validate the origin of requests, allowing malicious actors to execute unauthorized administrative actions on behalf of authenticated administrators. The issue manifests through three distinct attack vectors that enable attackers to manipulate user accounts within the system, making it particularly dangerous for organizations managing multiple user accounts through the admin console.
The technical implementation of this CSRF vulnerability occurs due to the absence of proper CSRF token validation within the Admin Console interface. According to CWE-352, this represents a classic cross-site request forgery weakness where the application fails to verify that requests originate from legitimate sources within the same session. The vulnerability specifically impacts three critical account management operations: adding new accounts, modifying existing account parameters, and removing user accounts from the system. Attackers can exploit this weakness by crafting malicious web pages or email content that, when visited by an authenticated administrator, automatically submits requests to the Zimbra Admin Console. The lack of effective referer header checks further compounds the issue, as the application does not adequately verify the source of incoming requests to ensure they originate from legitimate administrative interfaces rather than external malicious domains.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it provides attackers with comprehensive administrative control over the email system. Organizations face significant risks including unauthorized account creation that could be used for phishing attacks or spam distribution, modification of existing accounts to redirect email traffic or alter permissions, and complete removal of user accounts that could disrupt business communications. This vulnerability directly violates the principle of least privilege and undermines the integrity of the administrative access controls. According to ATT&CK framework, this represents a privilege escalation technique where attackers leverage existing administrative sessions to perform actions that would normally require explicit administrative credentials. The attack surface is particularly concerning because administrators often maintain persistent sessions while performing routine administrative tasks, making them vulnerable to exploitation through simple web page visits or email links.
Mitigation strategies for this vulnerability require immediate implementation of proper CSRF protection mechanisms within the Zimbra Admin Console. Organizations should upgrade to Zimbra Collaboration version 8.6.0 Patch 8 or later, which includes the necessary security patches addressing the CSRF token validation issues. Additionally, administrators should implement network-level protections including firewall rules that restrict access to the Admin Console to trusted IP ranges, and consider implementing additional authentication layers such as two-factor authentication for administrative access. The solution must incorporate robust CSRF token generation and validation mechanisms that ensure each request contains a unique, unpredictable token that is verified against the user's session. Security monitoring should be enhanced to detect unusual administrative activities that could indicate CSRF exploitation attempts. Organizations should also conduct regular security assessments of their email infrastructure to identify similar vulnerabilities in other administrative interfaces and ensure proper input validation and session management practices are consistently applied across all web applications.