CVE-2026-63919 xfrm: input: hold netns during deferred transport reinjection
A use-after-free vulnerability in the Linux kernel's xfrm input handling allows attackers to cause denial of service or potentially execute code via deferred transport reinjection.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-63919?
CVE-2026-63919 is a high-severity use after free vulnerability in Linux kernel, published on 19 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
xfrm: input: hold netns during deferred transport reinjection
Transport-mode reinjection stores a struct net pointer in skb->cb and uses it later from xfrm_trans_reinject(). That pointer must stay valid until the deferred callback runs.
Take a netns reference when queueing deferred reinjection work and drop it after the callback completes. Use maybe_get_net() so the queueing path does not revive a namespace that is already being torn down.
This keeps the existing workqueue design and fixes the netns lifetime handling in one place for all users of xfrm_trans_queue_net().
Weakness: CWE-416
Which versions are affected by CVE-2026-63919?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-63919?
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-2026-63919 being exploited?
There is no known exploitation of CVE-2026-63919 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-63919, DEBIAN-CVE-2026-63919, GHSA-c9j4-h9xp-p2mj, ROOT-OS-UBUNTU-2204-CVE-2026-63919, UBUNTU-CVE-2026-63919.