CVE-2023-53600: tunnels: fix kasan splat when generating ipv4 pmtu error

Severity: high (CVSS 7.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-10-04 · updated 2026-10-15
Weakness: CWE-125

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.

Affected products

Linux kernel: from 5.9 before 5.10.191; from 5.11 before 5.15.127; from 5.16 before 6.1.46; from 6.2 before 6.4.11; 6.5-rc1, 6.5-rc2, 6.5-rc3, 6.5-rc4, 6.5-rc5 — fixed in 5.10.191, 5.15.127, 6.1.46, 6.4.11

How to fix

Upgrade to a fixed version: Linux kernel 5.10.191, 5.15.127, 6.1.46, 6.4.11. Check the vendor advisory for mitigations.

References

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