CVE-2019-1892 in Small Business 200 Managed Switch
Summary
by MITRE
A vulnerability in the Secure Sockets Layer (SSL) input packet processor of Cisco Small Business 200, 300, and 500 Series Managed Switches could allow an unauthenticated, remote attacker to cause a memory corruption on an affected device. The vulnerability is due to improper validation of HTTPS packets. An attacker could exploit this vulnerability by sending a malformed HTTPS packet to the management web interface of the affected device. A successful exploit could allow the attacker to cause an unexpected reload of the device, resulting in a denial of service (DoS) condition.
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Analysis
by VulDB Data Team • 10/18/2023
The vulnerability identified as CVE-2019-1892 represents a critical security flaw within the SSL input packet processing mechanism of Cisco Small Business 200, 300, and 500 Series Managed Switches. This issue resides in the device's handling of HTTPS traffic and specifically affects the management web interface that administrators use to configure and monitor network devices. The vulnerability stems from inadequate validation procedures that fail to properly examine incoming HTTPS packets before processing them within the switch's memory management system. This weakness creates an exploitable condition that allows unauthorized remote attackers to manipulate the device's operational state through carefully crafted network traffic.
The technical implementation of this vulnerability occurs when an attacker sends malformed HTTPS packets to the affected switch's management interface. These packets bypass normal validation checks and trigger memory corruption within the device's processing engine. The improper validation mechanism fails to adequately sanitize input data, allowing maliciously constructed packet payloads to cause unexpected behavior in the switch's memory allocation and processing routines. The vulnerability specifically targets the SSL/TLS processing layer where HTTPS traffic is handled, making it particularly dangerous as it operates at the network layer where management communications occur. This flaw aligns with CWE-129, which addresses improper validation of input boundaries, and represents a classic case of buffer overflow or memory corruption vulnerability that can be exploited through malformed network traffic.
The operational impact of this vulnerability extends beyond simple denial of service conditions, though that remains the primary concern. When successfully exploited, the memory corruption causes the affected switch to unexpectedly reload its operating system, effectively disrupting network connectivity and management access for the duration of the restart process. Network administrators lose visibility into their managed switches during this downtime, potentially creating windows for further attacks or service interruptions. The vulnerability's remote nature means attackers do not require physical access or network credentials to exploit the flaw, making it particularly dangerous for unsecured network environments. This condition directly maps to ATT&CK technique T1499.004, which describes network denial of service attacks, and represents a significant threat to network availability and operational continuity.
Mitigation strategies for CVE-2019-1892 should prioritize immediate firmware updates from Cisco to address the underlying validation flaws in the SSL packet processing. Network administrators should also implement network segmentation to isolate management interfaces from untrusted networks, while enabling access controls that restrict management traffic to specific IP addresses or ranges. Additional protective measures include configuring firewall rules to block unnecessary HTTPS traffic to switch management interfaces and implementing network monitoring to detect anomalous packet patterns that might indicate exploitation attempts. The vulnerability highlights the importance of proper input validation in network device firmware and underscores the need for robust security testing of SSL/TLS implementations in embedded network appliances. Organizations should also consider implementing intrusion detection systems that can identify malformed HTTPS traffic patterns and provide early warning of potential exploitation attempts against their network infrastructure.