CVE-2015-6285 in Email Security Appliance
Summary
by MITRE
Format string vulnerability in Cisco Email Security Appliance (ESA) 7.6.0 and 8.0.0 allows remote attackers to cause a denial of service (memory overwrite or service outage) via format string specifiers in an HTTP request, aka Bug ID CSCug21497.
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Analysis
by VulDB Data Team • 12/09/2017
The vulnerability identified as CVE-2015-6285 represents a critical format string vulnerability within Cisco Email Security Appliance versions 7.6.0 and 8.0.0. This flaw resides in the web-based management interface of the ESA system, which serves as a crucial component for email security operations within enterprise environments. The vulnerability stems from improper input validation and handling of format string specifiers within HTTP request processing, creating a pathway for malicious actors to exploit the system's memory management functions. The affected Cisco Email Security Appliance operates as a comprehensive email security solution that filters and protects against spam, malware, and other email-based threats, making it a prime target for attackers seeking to disrupt critical communication infrastructure.
The technical exploitation of this vulnerability occurs when remote attackers submit specially crafted HTTP requests containing format string specifiers to the ESA web interface. These malformed requests trigger improper memory handling within the application's string processing functions, leading to potential memory overwrite conditions or complete service outages. The vulnerability specifically affects the application's ability to properly interpret and process user-supplied input through format string functions, which are commonly used for generating output messages and logging activities. Attackers can leverage this weakness to cause the system to behave unpredictably, potentially leading to crashes, memory corruption, or complete denial of service conditions that prevent legitimate users from accessing email security services. This type of vulnerability falls under CWE-134, which specifically addresses the use of format strings inappropriately, and aligns with ATT&CK technique T1499.004 for network disruption and service availability attacks.
The operational impact of CVE-2015-6285 extends beyond simple service interruption, as the Email Security Appliance serves as a critical gateway for email traffic within enterprise networks. When compromised, the vulnerability can result in complete email service outages, potentially affecting thousands of users within an organization and disrupting business operations. The remote nature of the attack means that adversaries do not require physical access or network proximity to exploit the vulnerability, making it particularly dangerous in environments where network segmentation may not be fully effective. Organizations relying on the ESA for email filtering and security services face significant risk of communication disruption, which could lead to productivity losses, compliance violations, and potential exposure to additional security threats during the service disruption period. The vulnerability's impact is compounded by the fact that email security appliances are often considered mission-critical infrastructure components that require high availability and reliability in enterprise environments.
Mitigation strategies for CVE-2015-6285 should prioritize immediate patching of affected systems with Cisco's official security updates, which address the underlying format string handling issues in the web interface components. Organizations should implement network segmentation to limit access to the ESA management interface, restricting access to trusted administrative networks and employing multi-factor authentication for privileged access. Network monitoring should be enhanced to detect unusual HTTP request patterns that might indicate exploitation attempts, while firewall rules should be configured to restrict unnecessary access to the appliance's web management ports. Additionally, regular security assessments and vulnerability scanning should be conducted to identify potential exploitation vectors and ensure that all security measures remain effective. Organizations should also maintain detailed incident response procedures specifically addressing email security appliance vulnerabilities, ensuring rapid response capabilities when such threats are detected in their environments. The remediation process should include comprehensive testing of patches in non-production environments before deployment to ensure that security updates do not introduce compatibility issues with existing email security configurations and policies.