CVE-2022-49654 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
net: dsa: qca8k: reset cpu port on MTU change
It was discovered that the Documentation lacks of a fundamental detail on how to correctly change the MAX_FRAME_SIZE of the switch.
In fact if the MAX_FRAME_SIZE is changed while the cpu port is on, the switch panics and cease to send any packet. This cause the mgmt ethernet system to not receive any packet (the slow fallback still works) and makes the device not reachable. To recover from this a switch reset is required.
To correctly handle this, turn off the cpu ports before changing the MAX_FRAME_SIZE and turn on again after the value is applied.
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Analysis
by VulDB Data Team • 10/23/2025
The vulnerability identified as CVE-2022-49654 resides within the Linux kernel's networking subsystem, specifically within the dsa (Distributed Switch Architecture) module that manages switch chip drivers including the qca8k driver for Qualcomm Atheros switch chips. This issue represents a critical design flaw in how the system handles maximum frame size changes on switch hardware, creating a scenario where normal network operations can lead to complete network outages. The vulnerability manifests when administrators or automated systems attempt to modify the maximum frame size parameter while the CPU port remains active, resulting in a system panic that renders the entire switch functionality inoperable.
The technical root cause of this vulnerability lies in the improper handling of CPU port states during maximum frame size modifications within the qca8k switch driver implementation. When the MAX_FRAME_SIZE parameter is altered without first disabling the CPU port, the switch chip enters an inconsistent state that triggers a panic condition. This panic prevents any packet transmission through the switch fabric, effectively cutting off all network communication including management traffic that relies on the CPU port for system administration. The documentation deficiency compounds this issue by failing to specify the required sequence of operations needed to safely modify frame size parameters, leaving administrators unaware of the critical prerequisite steps necessary to prevent system crashes.
The operational impact of this vulnerability extends beyond simple network disruption to encompass complete system unreachability and potential service degradation. Network administrators attempting routine maintenance or configuration changes risk causing complete network outages that require manual intervention and system resets to recover from. The slow fallback mechanism remains functional, allowing some basic network functionality to persist, but this is insufficient for proper system management and monitoring. The requirement for a full switch reset represents a significant operational burden, potentially causing extended downtime for network services and requiring careful coordination of maintenance windows. This vulnerability directly impacts network infrastructure reliability and can affect mission-critical systems where network availability is paramount.
The recommended mitigation strategy involves implementing a proper sequence of operations that disables the CPU port before frame size modifications and re-enables it afterward. This approach aligns with security best practices for configuration management and system stability. Organizations should update their network management procedures to include explicit steps for handling maximum frame size changes, ensuring that all administrative actions include proper port state management. System administrators must be trained on the correct procedures to prevent accidental triggering of this panic condition. Additionally, automated network management systems should be updated to incorporate these safety checks before executing frame size modification commands, reducing the risk of human error in configuration changes. This vulnerability demonstrates the importance of comprehensive documentation and proper state management in network infrastructure components, aligning with CWE-691 (Insufficient Control Flow Management) and ATT&CK technique T1059.001 (Command and Scripting Interpreter) where improper system state handling can lead to complete system compromise.