CVE-2026-98490 net: openvswitch: conntrack: fix helper UAF due to extensions realloc
A use-after-free in the Linux kernel Open vSwitch conntrack module allows attackers to execute code or escalate privileges 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-2026-98490?
CVE-2026-98490 is a critical 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: fix helper UAF due to extensions realloc
While calling the helpers, a raw pointer to the extensions area is wired into expectations list:
-> nf_ct_helper() -> helper->help() -> nf_ct_expect_related_report() -> nf_ct_expect_insert() -> hlist_add_head_rcu(&exp->lnode, &master_help->expectations)
In case the connection is not confirmed yet, more extensions can be added afterwards with *_ext_add() calls reallocating the extension space and leaving the now invalid pointer in the expectations list that is later accessed while removing the expectation.
Make sure that helpers are called at the end after all the other extensions are already added.
Note that the helper rejection now leaves the mark and labels set, but that's not different from how the NAT was handled before or how the mark and the labels were handled on confirmation failure. And there are no atomicity guarantees provided by the API anyway.
Which versions are affected by CVE-2026-98490?
How do I fix CVE-2026-98490?
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-2026-98490 being exploited?
There is no known exploitation of CVE-2026-98490 in the wild and no public exploit code.
Sources
Also known as AZL-108815, BELL-CVE-2026-98490, DEBIAN-CVE-2026-98490, GHSA-4r7h-j2g8-7vfx, UBUNTU-CVE-2026-98490.