CVE-2016-1486 in Email Security Appliance
Summary
by MITRE
A vulnerability in the email attachment scanning functionality of the Advanced Malware Protection (AMP) feature of Cisco AsyncOS Software for Cisco Email Security Appliances could allow an unauthenticated, remote attacker to cause an affected device to stop scanning and forwarding email messages due to a denial of service (DoS) condition. Affected Products: This vulnerability affects Cisco AsyncOS Software releases 9.7.1 and later, prior to the first fixed release, for both virtual and hardware Cisco Email Security Appliances, if the AMP feature is configured to scan incoming email attachments. More Information: CSCuy99453. Known Affected Releases: 9.7.1-066. Known Fixed Releases: 10.0.0-125 9.7.1-207 9.7.2-047.
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Analysis
by VulDB Data Team • 10/14/2024
The vulnerability described in CVE-2016-1486 represents a critical denial of service weakness within Cisco's Advanced Malware Protection functionality, specifically affecting the email security appliance's ability to process incoming attachments. This flaw exists within the Cisco AsyncOS Software version 9.7.1 and subsequent releases, impacting both virtual and hardware implementations of the Cisco Email Security Appliances. The vulnerability stems from a design flaw in how the system handles email attachment scanning processes, creating an exploitable condition that allows unauthorized remote attackers to disrupt normal email operations without requiring authentication credentials.
The technical mechanism behind this vulnerability involves a specific flaw in the attachment scanning subsystem that causes the affected system to become unresponsive when processing certain malformed or crafted email attachments. When an attacker sends a specially constructed email message containing maliciously formatted attachments, the AMP feature's processing logic fails to properly handle the input, leading to a complete cessation of email scanning and forwarding capabilities. This condition effectively renders the email security appliance non-functional for its primary purpose of protecting against malware threats, creating a significant operational disruption that can persist until manual intervention or system restart occurs.
From an operational perspective, this vulnerability presents a severe risk to organizations relying on Cisco Email Security Appliances for their email protection infrastructure. The attack scenario involves an unauthenticated remote attacker who can exploit this weakness to bring down email services across affected deployments, potentially causing business disruption and leaving email traffic unprotected against malware threats during the DoS period. The impact extends beyond simple service interruption as it compromises the fundamental security posture of the organization's email infrastructure, potentially allowing attackers to bypass other security controls while the appliance remains non-operational.
The vulnerability aligns with CWE-400, which categorizes "Uncontrolled Resource Consumption" as a common weakness in software systems, where an attacker can manipulate resource usage to cause system instability or failure. From the MITRE ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to "Endpoint Denial of Service" and demonstrates how attackers can leverage system weaknesses to create persistent service disruptions. The affected software versions indicate that this issue was present in the 9.7.1 release and its subsequent builds, making it a long-standing problem that required multiple patch releases to address properly.
Organizations should implement immediate mitigation strategies including applying the recommended software updates to versions 10.0.0-125, 9.7.1-207, and 9.7.2-047 as specified in the vulnerability advisory. Network administrators should also consider implementing additional monitoring and alerting mechanisms to detect potential exploitation attempts, as well as maintaining redundant email security infrastructure where possible. The patching process should be carefully coordinated to ensure minimal disruption to email services while addressing the underlying DoS vulnerability. Additionally, organizations may want to implement temporary workarounds such as temporarily disabling the AMP feature for attachment scanning if immediate patching is not feasible, though this approach reduces overall security coverage and should only be considered as a temporary measure.