CVE-2025-21761

CVE-2025-21761 is a use-after-free (UAF) vulnerability in the Linux kernel's Open vSwitch (OVS) implementation, specifically within the ovs_vport_cmd_fill_info() function. This function could be invoked without proper Reverse Path Network Link (RTNL) or Read-Copy Update (RCU) protection, leading to potential UAF conditions. The issue, classified under CWE-416, affects Linux kernel versions incorporating Open vSwitch and carries a CVSS v3.1 base score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).

A local attacker with low privileges can exploit this vulnerability with low complexity and no user interaction required. Successful exploitation could result in high-impact consequences, including unauthorized access to sensitive data (high confidentiality impact), modification of kernel state (high integrity impact), and system denial of service or crashes (high availability impact), potentially elevating privileges within the kernel context.

Mitigation is available through patches applied to Linux kernel stable branches, as detailed in the referenced commits: 5828937742af74666192835d657095d95c53dbd0, 7e01abc34e87abd091e619161a20f54ed4e3e2da, 8ec57509c36c8b9a23e50b7858dda0c520a2d074, 90b2f49a502fa71090d9f4fe29a2f51fe5dff76d, and a849a10de5e04d798f7f286a2f1ca174719a617a. These commits implement RCU protection and utilize dev_net_rcu() to prevent the UAF by ensuring safe access to network device structures. Security practitioners should update affected kernel versions promptly, particularly in environments using Open vSwitch for virtual networking.