CVE-2017-3873 in Aironet
Summary
by MITRE
A vulnerability in the Plug-and-Play (PnP) subsystem of the Cisco Aironet 1800, 2800, and 3800 Series Access Points running a Lightweight Access Point (AP) or Mobility Express image could allow an unauthenticated, adjacent attacker to execute arbitrary code with root privileges. The vulnerability is due to insufficient validation of PnP server responses. The PnP feature is only active while the device does not contain a configuration, such as a first time boot or after a factory reset has been issued. An attacker with the ability to respond to PnP configuration requests from the affected device can exploit the vulnerability by returning malicious PnP responses. If a Cisco Application Policy Infrastructure Controller - Enterprise Module (APIC-EM) is available on the network, the attacker would need to exploit the issue in the short window before a valid PnP response was received. If successful, the attacker could gain the ability to execute arbitrary code with root privileges on the underlying operating system of the device. Cisco has confirmed that the only vulnerable software version is 8.3.102.0. Cisco Bug IDs: CSCvb42386.
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Analysis
by VulDB Data Team • 12/22/2020
The vulnerability described in CVE-2017-3873 represents a critical security flaw within the Plug-and-Play subsystem of Cisco Aironet 1800, 2800, and 3800 Series Access Points. This issue specifically affects devices running Lightweight Access Point or Mobility Express images, creating a pathway for unauthorized code execution that could compromise the entire network infrastructure. The vulnerability stems from insufficient validation mechanisms within the PnP server response handling process, making it particularly dangerous given the privileged access level that can be gained through exploitation.
The technical exploitation of this vulnerability occurs through a man-in-the-middle attack vector where an adjacent attacker can intercept PnP configuration requests from the affected access point. During the initial boot process or after factory reset operations, the device actively seeks PnP configuration responses from network servers, creating a narrow window of opportunity for attackers to inject malicious responses. The flaw lies in the lack of proper input validation and response authentication mechanisms that should verify the legitimacy of configuration data received from remote servers. This vulnerability is classified under CWE-20 as a weakness related to improper input validation, specifically in the context of network protocol handling and configuration management.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it allows attackers to execute arbitrary code with root privileges on the underlying operating system of the affected devices. This level of access provides complete control over the access point's functionality, enabling attackers to modify network configurations, intercept wireless traffic, or establish persistent backdoors within the network infrastructure. The timing aspect of the vulnerability is particularly significant since it only remains exploitable during the initial configuration phase, making it a critical target for attackers who can position themselves within the network to intercept these specific communication windows. The vulnerability affects only version 8.3.102.0 of the affected software, as documented in Cisco Bug ID CSCvb42386, highlighting the importance of proper software version management and patching procedures.
Mitigation strategies for this vulnerability require immediate implementation of network segmentation measures to prevent unauthorized access to the affected devices during their vulnerable boot phases. Network administrators should implement strict access controls and ensure that only trusted servers can respond to PnP requests from these devices. The most effective remediation involves upgrading the affected access point software to versions that address the PnP response validation issues, though this requires careful planning to avoid service disruption. Organizations should also consider implementing network monitoring solutions that can detect anomalous PnP traffic patterns, as this vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter execution through legitimate system processes. Additionally, the vulnerability demonstrates the importance of network security controls in preventing lateral movement and privilege escalation attacks that could compromise enterprise wireless infrastructure.