CVE-2016-9220 in Mobility Express 2800
Summary
by MITRE
A Denial of Service Vulnerability in 802.11 ingress packet processing of the Cisco Mobility Express 2800 and 3800 Access Points (APs) could allow an unauthenticated, adjacent attacker to cause the connection table to be full of invalid connections and be unable to process new incoming requests. More Information: CSCvb66659. Known Affected Releases: 8.2(130.0). Known Fixed Releases: 8.2(131.10) 8.2(131.6) 8.2(141.0) 8.3(104.56) 8.4(1.88) 8.4(1.91).
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Analysis
by VulDB Data Team • 05/14/2026
The vulnerability identified as CVE-2016-9220 represents a critical denial of service weakness within Cisco Mobility Express 2800 and 3800 access point implementations that specifically targets the 802.11 ingress packet processing mechanism. This flaw exists in the wireless access point's handling of incoming network frames and creates a condition where malicious actors can exploit the connection table management system to overwhelm it with invalid entries. The vulnerability manifests when an unauthenticated attacker positioned within the wireless coverage area of the affected access points can craft and transmit specially formatted 802.11 frames that trigger the device to allocate resources for connections that will never be properly established or maintained. This attack vector operates under the principle that the access point's connection table lacks proper validation mechanisms to distinguish between legitimate and malicious connection attempts, allowing the attacker to consume available connection slots rapidly. The issue falls under CWE-400 which specifically addresses unspecified denial of service vulnerabilities, and aligns with ATT&CK technique T1499.002 related to network denial of service attacks that target network infrastructure components. The affected releases including 8.2(130.0) demonstrate that this weakness was present in a specific firmware version that failed to implement adequate resource management controls during packet processing operations.
The technical exploitation of this vulnerability occurs through the manipulation of 802.11 frame structures that are processed by the access point's wireless controller functionality. When the affected access point receives these malformed or crafted frames, the ingress processing logic does not properly validate the connection state information contained within the frames, leading to the creation of invalid connection entries in the device's internal connection table. The connection table serves as a critical data structure that maintains information about active wireless sessions and their associated resources, and when this table becomes saturated with invalid entries, legitimate wireless users experience complete service disruption. The attacker does not require any authentication credentials to exploit this weakness, making it particularly dangerous as it can be executed from adjacent wireless coverage areas without the need for network access or prior authorization. This adjacency requirement places the vulnerability in the ATT&CK matrix under T1046 which covers network service scanning and reconnaissance activities, though the actual exploitation does not require the attacker to perform active scanning. The flaw essentially creates a resource exhaustion condition where the connection table reaches its maximum capacity due to the accumulation of invalid connection entries, preventing the legitimate processing of new wireless connection requests.
The operational impact of CVE-2016-9220 extends beyond simple service disruption to create a complete denial of wireless connectivity for legitimate users within the affected access point's coverage area. When the connection table becomes full of invalid entries, the access point cannot process new wireless association requests, effectively blocking all new wireless clients from connecting to the network while potentially maintaining connectivity for existing users who have already established sessions. This condition can persist until the access point is manually reset or the affected firmware version is upgraded to one that contains the necessary fixes. The vulnerability's impact is particularly severe in enterprise environments where wireless access points serve critical business functions, as it can disrupt operations, create security gaps, and potentially allow unauthorized access to network resources if legitimate users are denied access. The affected access points must maintain a balance between processing legitimate wireless frames and managing connection state information, and this vulnerability exploits the gap in validation mechanisms that should prevent malformed or malicious connection attempts from consuming critical resources. Organizations may experience cascading effects where wireless outages impact productivity, customer service operations, and business continuity, particularly in environments where wireless connectivity is essential for business operations.
Cisco addressed this vulnerability through multiple firmware releases including 8.2(131.10), 8.2(131.6), 8.2(141.0), 8.3(104.56), 8.4(1.88), and 8.4(1.91) which introduced enhanced validation mechanisms for 802.11 ingress packet processing. The mitigations implemented in these firmware versions focus on strengthening the connection table management logic to properly validate incoming connection requests and reject malformed frames before allocating connection table resources. Network administrators should prioritize upgrading affected access points to these patched firmware versions to eliminate the vulnerability. Additional mitigations include implementing wireless intrusion prevention systems that can detect and block suspicious wireless traffic patterns, configuring access point security policies to limit the rate of connection requests, and monitoring wireless network performance for signs of connection table saturation. The vulnerability's classification under CWE-400 and its exploitation pattern align with common denial of service attack methodologies that target resource management components within network infrastructure devices. Organizations should also consider implementing network segmentation strategies to limit the impact of such attacks and ensure that wireless access points are properly monitored for unusual connection patterns that might indicate exploitation attempts. The fix essentially closes the gap in the access point's ingress packet processing logic by introducing proper validation checks that prevent invalid connection entries from being created in the connection table, thereby maintaining the integrity of the wireless network infrastructure and ensuring continued service availability for legitimate users.