---
cve: "CVE-2026-64538"
severity: "LOW"
cvss: 3.1
epss: "18%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-07-27 21:17:06"
tags: [cve, security, low]
source: tsecurity.de CVE-Dossier
exported: "2026-09-13T16:43:12+02:00"
---

# CVE-2026-64538

> 3.1 LOW

## Beschreibung

In the Linux kernel, the following vulnerability has been resolved:

ipv6: Fix null-ptr-deref in fib6_nh_mtu_change().

fib6_nh_mtu_change() re-fetches idev via __in6_dev_get(arg->dev) and
dereferences idev->cnf.mtu6 without a NULL check. addrconf_ifdown()
clears dev->ip6_ptr with RCU_INIT_POINTER() after rt6_disable_ip() has
released tb6_lock, so the RA-driven MTU walk can observe a NULL idev and
oops. The caller rt6_mtu_change_route() guards its own __in6_dev_get(),
but this re-fetch is unguarded; nexthop-backed routes survive
addrconf_ifdown()'s flush, so the walk still reaches it after ip6_ptr is
nulled.

Return 0 when idev is NULL, matching rt6_mtu_change_route() and the
fib6_mtu() fix in commit 5ad509c1fdad ("ipv6: Fix null-ptr-deref in
fib6_mtu().").

  Oops: general protection fault, ... KASAN: null-ptr-deref in range
        [0x00000000000002a8-0x00000000000002af]
  RIP: 0010:fib6_nh_mtu_change+0x203/0x990
   rt6_mtu_change_route+0x141/0x1d0
   __fib6_clean_all+0xd0/0x160
   rt6_mtu_change+0xb4/0x100
   ndisc_router_discovery+0x24b5/0x2cb0
   icmpv6_rcv+0x12e9/0x1710
   ipv6_rcv+0x39b/0x410

## Patch verfügbar (OSV)

- Kernel ≥ 5.10.261
- Kernel ≥ 5.15.212
- Kernel ≥ 6.1.178
- Kernel ≥ 6.6.145
- Kernel ≥ 6.12.97
- Kernel ≥ 6.18.40
- Kernel ≥ 7.1.5

## Referenzen

- <https://git.kernel.org/stable/c/d08d019f2f43a6f9a71e81868bbc326b3afaf37b>
- <https://git.kernel.org/stable/c/1451deca9896957159f0666520a792c1b861af4f>
- <https://git.kernel.org/stable/c/b2c70dd3326809429b709a9c7e9220d29923051a>
- <https://git.kernel.org/stable/c/302d57ed7872838b40e56a868fb4c7da7da606e9>
- <https://git.kernel.org/stable/c/80600b5d0f3ecb9324120dc95b5e915130f516c5>
- <https://git.kernel.org/stable/c/b0d0eb13a0441a8ebf4f227843deaf494f1e2c33>
- <https://git.kernel.org/stable/c/6428634f7a0b7878144b4925c37856bef3224967>
- <https://git.kernel.org/stable/c/46c3b8191aad3d032776bf3bebf03efdf5f4b905>
- <https://cert-portal.siemens.com/productcert/html/ssa-019113.html>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-64538) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_