CVE-2014-6336 in Exchange
Summary
by MITRE
Outlook Web App (OWA) in Microsoft Exchange Server 2013 SP1 and Cumulative Update 6 does not properly validate redirection tokens, which allows remote attackers to redirect users to arbitrary web sites and spoof the origin of e-mail messages via unspecified vectors, aka "Exchange URL Redirection Vulnerability."
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Analysis
by VulDB Data Team • 03/01/2022
The CVE-2014-6336 vulnerability represents a critical security flaw in Microsoft Exchange Server's Outlook Web App component that specifically affects versions 2013 SP1 and Cumulative Update 6. This vulnerability stems from insufficient validation of redirection tokens within the web application interface, creating a pathway for malicious actors to manipulate user navigation and message authenticity. The flaw operates at the application layer of the OSI model, specifically within the presentation and application layers where user interface elements interact with backend services to process email operations and web navigation requests.
The technical implementation of this vulnerability exploits the improper validation of URL redirection parameters that are commonly used in web applications for session management and navigation purposes. Attackers can craft malicious URLs containing specially formatted redirection tokens that bypass the normal validation checks implemented by Exchange Server's OWA. These tokens typically contain encoded URLs or URI references that, when processed by the vulnerable application, trigger unintended redirects to attacker-controlled domains. The vulnerability's root cause aligns with CWE-601, which specifically addresses URL redirection vulnerabilities where applications fail to properly validate or sanitize redirection parameters, and it also maps to ATT&CK technique T1566.001 for the use of spearphishing with links that redirect to malicious sites.
The operational impact of this vulnerability extends beyond simple phishing attacks, as it enables sophisticated social engineering campaigns that can appear highly legitimate to end users. When users receive compromised email messages containing malicious links, the redirection mechanism can make the phishing sites appear to originate from trusted Exchange servers, significantly increasing the success rate of such attacks. Additionally, the vulnerability allows attackers to spoof the origin of email messages, potentially enabling them to impersonate legitimate senders within corporate networks and bypass security controls designed to detect suspicious email sources. This capability particularly affects organizations that rely on Exchange Server for email communication and may have insufficient email filtering mechanisms to detect such sophisticated redirection attacks.
Organizations affected by this vulnerability should immediately implement multiple layers of defense to mitigate potential exploitation. The primary recommendation involves applying the relevant security patches provided by Microsoft through their regular update cycles, specifically targeting the Cumulative Update that addresses this particular flaw. Network administrators should also implement strict URL filtering policies at perimeter devices and within the organization's email security infrastructure to block suspicious redirection attempts. Additionally, user education programs should emphasize the importance of verifying URL destinations before clicking on email links, particularly when dealing with unexpected or unsolicited messages. The vulnerability's characteristics make it particularly dangerous in environments where users may not be trained to identify subtle differences between legitimate and malicious URLs, highlighting the importance of comprehensive security awareness training programs. Organizations should also consider implementing email authentication mechanisms such as SPF, DKIM, and DMARC to provide additional protection against message spoofing attacks that could leverage this vulnerability.