CVE-2023-53600 tunnels: fix kasan splat when generating ipv4 pmtu error
A kernel bug in tunnel handling causes a slab-out-of-bounds read when generating ICMP errors, leading to system crashes or hangs.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-53600?
CVE-2023-53600 is a critical memory corruption vulnerability in Linux kernel, published on 4 Oct 2025. 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:
tunnels: fix kasan splat when generating ipv4 pmtu error
If we try to emit an icmp error in response to a nonliner skb, we get
BUG: KASAN: slab-out-of-bounds in ip_compute_csum+0x134/0x220 Read of size 4 at addr ffff88811c50db00 by task iperf3/1691 CPU: 2 PID: 1691 Comm: iperf3 Not tainted 6.5.0-rc3+ #309 [..] kasan_report+0x105/0x140 ip_compute_csum+0x134/0x220 iptunnel_pmtud_build_icmp+0x554/0x1020 skb_tunnel_check_pmtu+0x513/0xb80 vxlan_xmit_one+0x139e/0x2ef0 vxlan_xmit+0x1867/0x2760 dev_hard_start_xmit+0x1ee/0x4f0 br_dev_queue_push_xmit+0x4d1/0x660 [..]
ip_compute_csum() cannot deal with nonlinear skbs, so avoid it. After this change, splat is gone and iperf3 is no longer stuck.
Weakness: CWE-125
Which versions are affected by CVE-2023-53600?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2023-53600?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2023-53600 being exploited?
There is no known exploitation of CVE-2023-53600 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2023-53600, DEBIAN-CVE-2023-53600, GHSA-qh3w-rq3m-fpq5, UBUNTU-CVE-2023-53600.