CVE-2017-6661 in Email Security Appliance
Summary
by MITRE
A vulnerability in the web-based management interface of Cisco Email Security Appliance (ESA) and Cisco Content Security Management Appliance (SMA) could allow an unauthenticated, remote attacker to conduct a cross-site scripting (XSS) attack against a user of the web-based management interface of an affected device, aka Message Tracking XSS. More Information: CSCvd30805 CSCvd34861. Known Affected Releases: 10.0.0-203 10.1.0-049.
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Analysis
by VulDB Data Team • 12/26/2020
The vulnerability identified as CVE-2017-6661 represents a critical cross-site scripting flaw within the web-based management interfaces of Cisco Email Security Appliance (ESA) and Cisco Content Security Management Appliance (SMA) products. This weakness specifically affects versions 10.0.0-203 and 10.1.0-049, creating a significant security risk for organizations relying on these email security solutions. The vulnerability stems from insufficient input validation and output encoding mechanisms within the message tracking functionality of the web interface, which fails to properly sanitize user-supplied data before rendering it in the browser context. This flaw allows an unauthenticated remote attacker to inject malicious scripts into the web interface, potentially compromising the security of authenticated users who interact with the affected management console.
The technical implementation of this vulnerability occurs when an attacker crafts malicious input through the message tracking feature, which then gets processed and displayed without proper sanitization. The flaw manifests in the web application's handling of user-provided parameters, particularly within the message tracking functionality where the application fails to implement adequate encoding or validation measures. This allows attackers to inject malicious JavaScript code that executes in the context of the victim's browser session when they access the management interface. The vulnerability is classified under CWE-79 as a Cross-Site Scripting flaw, which represents one of the most common web application security vulnerabilities. The attack vector requires no authentication, making it particularly dangerous as it can be exploited by anyone with network access to the affected appliance's management interface, aligning with ATT&CK technique T1212 for exploitation of web application vulnerabilities.
The operational impact of this vulnerability extends beyond simple script execution, as it can potentially enable attackers to perform session hijacking, steal administrative credentials, or manipulate the security appliance's configuration. When an authenticated administrator accesses the vulnerable interface, the malicious script executes in their browser context, potentially allowing attackers to perform actions with the privileges of the logged-in user. This could lead to complete compromise of the email security infrastructure, enabling attackers to bypass security controls, monitor email traffic, modify security policies, or even redirect email flows to malicious destinations. The vulnerability also creates potential for privilege escalation scenarios where attackers could leverage the XSS to gain elevated access to the appliance's underlying system. Organizations using these appliances face significant risk of data breaches, email spoofing, and disruption of email services, as the compromised management interface provides attackers with direct access to critical email security controls and configurations.
Mitigation strategies for CVE-2017-6661 should prioritize immediate implementation of official Cisco patches and updates, as the vendor released security advisories addressing this specific vulnerability. Organizations should implement network segmentation to restrict access to the appliance's management interfaces, limiting exposure to trusted administrative networks only. Additional protective measures include implementing web application firewalls to detect and block malicious script injection attempts, enabling strict content security policies within the browser context, and conducting regular security assessments of the web interface components. Administrators should also consider disabling unnecessary web interface features, implementing multi-factor authentication for management access, and monitoring web application logs for suspicious activity. The vulnerability demonstrates the importance of input validation and output encoding practices in web application development, highlighting the need for comprehensive security testing throughout the software development lifecycle. Organizations should also review their incident response procedures to ensure they can quickly detect and respond to exploitation attempts, as the vulnerability's low attack threshold makes it particularly attractive to automated attack tools. Regular security awareness training for administrators can help identify potential exploitation attempts and maintain vigilance against social engineering components that might accompany such attacks.