CVE-2014-8016 in IronPort Email Security Appliance
Summary
by MITRE
The Cisco IronPort Email Security Appliance (ESA) allows remote attackers to cause a denial of service (CPU consumption) via long Subject headers in e-mail messages, aka Bug ID CSCzv93864.
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Analysis
by VulDB Data Team • 03/09/2019
The Cisco IronPort Email Security Appliance ESA presents a significant denial of service vulnerability identified as CVE-2014-8016, which stems from inadequate handling of email message headers. This vulnerability specifically targets the processing of Subject headers within incoming email messages, creating a condition where malformed or excessively long Subject fields can trigger abnormal CPU consumption patterns. The flaw manifests when the appliance attempts to parse and process email messages containing unusually lengthy Subject headers, leading to resource exhaustion that ultimately results in system unresponsiveness or complete service interruption. The vulnerability affects multiple versions of the Cisco IronPort ESA software and represents a critical weakness in the appliance's input validation and header processing mechanisms.
This vulnerability operates through a classic buffer overflow and processing inefficiency pattern that falls under CWE-129, which addresses insufficient validation of the length or magnitude of input data. The attack vector requires remote exploitation through the submission of specially crafted email messages containing extended Subject headers, making it particularly dangerous in email security environments where appliances must process thousands of messages per second. The system's failure to properly validate and limit the processing of Subject header content creates a condition where CPU resources become consumed in an uncontrolled manner, effectively rendering the appliance unable to process legitimate email traffic. The vulnerability is classified as a resource exhaustion attack that operates at the application layer, targeting the core processing functions of the email security appliance.
The operational impact of CVE-2014-8016 extends beyond simple service disruption to create substantial business continuity concerns for organizations relying on Cisco IronPort ESA for email security. When exploited, the vulnerability can cause complete system paralysis, requiring manual intervention to restore normal operations and potentially leading to extended downtime during which email services become unavailable. Organizations may experience cascading effects as email delivery systems fail, impacting communication workflows and potentially exposing sensitive data transmission gaps during the service outage. The vulnerability particularly affects environments with high email throughput where the appliance's processing capacity is already under strain, making the impact more severe and recovery more complex. The attack requires minimal technical expertise to execute, making it a preferred method for adversaries seeking to disrupt email services without requiring sophisticated attack infrastructure.
Mitigation strategies for CVE-2014-8016 should include immediate implementation of software patches provided by Cisco, which address the specific header processing flaw. Organizations should also implement email filtering rules that limit Subject header length to prevent exploitation, utilizing the appliance's built-in message filtering capabilities to automatically reject or truncate excessively long headers. Network administrators should monitor CPU utilization patterns and implement alerting mechanisms to detect unusual resource consumption that may indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a critical security gap that organizations must address through both immediate patching and ongoing monitoring. Additionally, implementing rate limiting and message size restrictions can provide additional defense-in-depth measures that reduce the attack surface and prevent exploitation while maintaining legitimate email service functionality.