CVE-2016-6358 in Email Security Appliance
Summary
by MITRE
A vulnerability in local FTP to the Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to cause a partial denial of service (DoS) condition when the FTP application unexpectedly quits. More Information: CSCux68539. Known Affected Releases: 9.1.0-032 9.7.1-000. Known Fixed Releases: 9.1.1-038.
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Analysis
by VulDB Data Team • 09/25/2024
The vulnerability identified as CVE-2016-6358 affects the Cisco Email Security Appliance (ESA) and represents a significant security weakness in the device's FTP service implementation. This issue manifests as a partial denial of service condition that can be triggered by unauthenticated remote attackers, making it particularly concerning for organizations relying on email security solutions. The vulnerability specifically impacts the FTP application component of the ESA, causing it to unexpectedly quit when certain conditions are met, thereby disrupting email services and potentially compromising organizational communication infrastructure.
The technical flaw resides in how the ESA handles FTP connections and processing, where improper error handling or resource management leads to application instability. When an attacker sends specifically crafted FTP requests or triggers certain FTP operations, the application fails to maintain proper state management or connection handling, resulting in the FTP service crashing and terminating unexpectedly. This behavior creates a partial denial of service scenario where email processing capabilities are impaired while other functions of the appliance may continue operating normally. The vulnerability demonstrates poor input validation and exception handling practices that are commonly associated with software reliability issues.
From an operational impact perspective, this vulnerability poses substantial risk to email security operations as it can disrupt critical communication infrastructure without requiring authentication credentials from the attacker. Organizations utilizing the affected ESA versions may experience intermittent email service disruptions, delayed email processing, or complete loss of FTP-based email handling capabilities. The partial nature of the denial of service means that while the appliance may remain operational, its email security functions become compromised, potentially allowing malicious actors to exploit the instability for further attacks or to disrupt business operations. The vulnerability also impacts the availability of email services, which can have cascading effects on organizational productivity and security posture.
Mitigation strategies for this vulnerability should prioritize immediate deployment of the fixed releases mentioned in the advisory, specifically version 9.1.1-038, which contains the necessary patches to address the FTP application instability. Organizations should conduct thorough testing of the updated firmware in non-production environments before rolling out the changes to ensure compatibility with existing email security configurations. Network segmentation and access controls should be implemented to limit exposure of the ESA to untrusted networks, while monitoring systems should be configured to detect unusual FTP activity patterns that might indicate exploitation attempts. Additionally, regular security assessments and vulnerability scanning should be performed to identify similar issues in other network security components, following the principles outlined in the CWE taxonomy for software reliability and error handling vulnerabilities. The remediation process should align with industry best practices for vulnerability management and incident response procedures as defined in various cybersecurity frameworks.