CVE-2026-89487

A flaw was found in openvswitch in the Linux kernel. This vulnerability occurs when the queue_userspace_packet() function incorrectly modifies a shared network packet buffer by stripping a critical flag. This action can lead to an unprivileged page-cache write, allowing a local attacker to modify data in memory that they should not have access to. This could potentially result in information disclosure or privilege escalation.

This vulnerability is rated as having an Important severity because an unprivileged local attacker can leverage improper packet buffer flag handling in the Open vSwitch subsystem to achieve unauthorized page-cache writes and elevate privileges. Successful exploitation requires specific zero-copy network traffic to traverse active Open vSwitch datapath flows, introducing configuration prerequisites. Default Red Hat Enterprise Linux installations do not load the Open vSwitch module unless explicitly configured or deployed in container platforms like Red Hat OpenShift.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

On systems where Open vSwitch is not needed, prevent the kernel module from loading:

1. Create a configuration file to disable module autoloading:

echo "install openvswitch /bin/true" > /etc/modprobe.d/disable-openvswitch.conf

2. If the module is currently loaded, reboot the system to unload it:

systemctl reboot

Warning: Applying this configuration requires a system reboot if the module is active. This workaround must not be applied to environments that rely on Open vSwitch (such as Red Hat OpenShift Container Platform or OpenStack), as disabling the module will disrupt cluster networking.