CVE-2026-74664 net: openvswitch: reallocate update replies for mismatched IDs

Q: Is CVE-2026-74664 being exploited?

There is no known exploitation of CVE-2026-74664 in the wild and no public exploit code.

Not scored Published 22 Aug 2026 Updated 22 Aug 2026

A local attacker can trigger a kernel crash in Open vSwitch by sending crafted flow update requests with mismatched identifiers.

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-2026-74664?

CVE-2026-74664 is a denial of service vulnerability in Linux, published on 22 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: reallocate update replies for mismatched IDs

ovs_flow_cmd_new() preallocates the optional reply skb before it takes ovs_mutex and before it knows which existing flow will be updated.

That is normally fine because the skb is sized from the request flow identifier. That identifier also becomes the inserted flow's identifier. For updates, however, a request with a UFID may miss the UFID lookup and then fall back to the flow key lookup. That lookup can legitimately find an existing key-identified flow. UFIDs are optional and the flow key is the primary identifier.

For echoed replies, ovs_flow_cmd_fill_info() writes the matched flow's identifier, not the request identifier used for the preallocation. A short request UFID can therefore leave too little room for the key identifier. The fill can then fail with -EMSGSIZE and hit the BUG_ON(error < 0) in the update path.

Once the update target has been resolved, reallocate the reply skb if the matched flow needs a larger reply than the request identifier allowed. Do this before replacing the actions so the request can still fail cleanly if the rare extra allocation fails.

Which versions are affected by CVE-2026-74664?

How do I fix CVE-2026-74664?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-74664 being exploited?