CVE-2026-63993 vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()
A use-after-free vulnerability in the Linux kernel VXLAN driver allows attackers to potentially execute code or escalate privileges by triggering a specific packet handling path.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-63993?
CVE-2026-63993 is a critical use after free vulnerability in Linux kernel, published on 19 Jul 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:
vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()
skb_tunnel_check_pmtu() can change skb->head.
Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF.
Use instead ip_hdr(skb) as done in drivers/net/bareudp.c and drivers/net/geneve.c.
Found by Sashiko.
Weakness: CWE-416
Which versions are affected by CVE-2026-63993?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-63993?
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-2026-63993 being exploited?
There is no known exploitation of CVE-2026-63993 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-63993, DEBIAN-CVE-2026-63993, GHSA-p6vc-4hvx-xvcw, ROOT-OS-UBUNTU-2204-CVE-2026-63993, UBUNTU-CVE-2026-63993.