CVE-2026-74465 net: openvswitch: fix potential UAF on meter attach failure
A use-after-free vulnerability in the Linux kernel's Open vSwitch module allows local attackers to execute arbitrary code or escalate privileges via crafted netlink messages.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74465?
CVE-2026-74465 is a high-severity use after free vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net: openvswitch: fix potential UAF on meter attach failure
While attaching a newly created meter attach_meter() function makes the new meter visible to other CPUs but can still fail afterwards. On failure, it detaches the meter back and returns an error.
However, this is an unexpected behavior for the ovs_meter_cmd_set() that uses a plain kfree(meter) on attach failure without waiting for RCU readers to stop using it, assuming it was never visible.
This is never a problem for ovs-vswitchd as it always creates meters before creating any flows that use them. But the UAF can be triggered with a custom application using uAPI:
BUG: KASAN: slab-use-after-free in ovs_meter_execute (net/openvswitch/meter.c:653) Read of size 8 at addr ffff88810d152650 by task meter/2508
Call Trace: ovs_meter_execute (net/openvswitch/meter.c:653) do_execute_actions (net/openvswitch/actions.c:1407) ovs_execute_actions (net/openvswitch/actions.c:1584) ovs_packet_cmd_execute (net/openvswitch/datapath.c:703) ... netlink_sendmsg (af_netlink.c:1900)
Allocated by task 2519: __kasan_kmalloc (mm/kasan/common.c:398 mm/kasan/common.c:415) ovs_meter_cmd_set (net/openvswitch/meter.c:422) ... netlink_sendmsg (af_netlink.c:1900)
Freed by task 2519: kfree (mm/slub.c:2705 mm/slub.c:6405 mm/slub.c:6720) ovs_meter_cmd_set (net/openvswitch/meter.c:479) ... netlink_sendmsg (af_netlink.c:1900)
Fix that by making sure attach_meter() doesn't make the meter visible until all the checks are done and the function can't fail anymore.
This also makes sure the "hash" value is calculated after the potential re-sizing of the table.
Reported by Trend Micro's Zero Day Initiative as ZDI-CAN-31642.
Which versions are affected by CVE-2026-74465?
How do I fix CVE-2026-74465?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-74465 being exploited?
There is no known exploitation of CVE-2026-74465 in the wild and no public exploit code.
Sources
Also known as AZL-96339, BELL-CVE-2026-74465, DEBIAN-CVE-2026-74465, GHSA-qwfg-529h-q8w8, UBUNTU-CVE-2026-74465.