CVE-2026-98491 net: openvswitch: conntrack: avoid modifying shared unconfirmed ct entry
A use-after-free vulnerability in the Linux kernel's Open vSwitch conntrack module allows attackers to potentially execute code or cause a denial of service via crafted network packets.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98491?
CVE-2026-98491 is a high-severity use after free vulnerability in Linux, published on 18 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net: openvswitch: conntrack: avoid modifying shared unconfirmed ct entry
In a case where skb with an unconfirmed ct entry gets cloned, we may end up committing both but with different sets of extensions.
The series of events:
1. The first clone wants to commit and runs the helpers wiring up the extension pointer into the expectation list. 2. Then it looses the confirmation keeping the entry unconfirmed. 3. Second clone now wants to commit labels and adds the new extension for that breaking the pointer in the expectation list causing UAF on the destruction path later.
While this is possible to trigger, there should be no practical network pipeline where committing both clones without modifications into the same zone is needed. So, let's just reset the entry in case for some reason we got an skb with a shared one during commit. This doesn't affect any known use cases, but avoids any potential problems with sharing and modification of the unconfirmed ct entry.
The fixes tag points to the introduction of helpers, since that's the main UAF trigger for the sharing.
Which versions are affected by CVE-2026-98491?
How do I fix CVE-2026-98491?
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-2026-98491 being exploited?
There is no known exploitation of CVE-2026-98491 in the wild and no public exploit code.
Sources
Also known as AZL-108710, BELL-CVE-2026-98491, DEBIAN-CVE-2026-98491, GHSA-xf3m-wp4c-wrgw, UBUNTU-CVE-2026-98491.