PT-2026-65213 · Linux · Linux

CVE-2026-64538 · Published 2026-07-27 · Updated 2026-07-27

NVD

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

Related Identifiers

CVE-2026-64538

Affected Products

Linux

References · 9

• https://nvd.nist.gov/vuln/detail/CVE-2026-64538 · Security Note
• https://git.kernel.org/stable/c/46c3b8191aad3d032776bf3bebf03efdf5f4b905 · Note
• https://git.kernel.org/stable/c/b0d0eb13a0441a8ebf4f227843deaf494f1e2c33 · Note
• https://git.kernel.org/stable/c/d08d019f2f43a6f9a71e81868bbc326b3afaf37b · Note
• https://git.kernel.org/stable/c/80600b5d0f3ecb9324120dc95b5e915130f516c5 · Note
• https://git.kernel.org/stable/c/6428634f7a0b7878144b4925c37856bef3224967 · Note
• https://git.kernel.org/stable/c/1451deca9896957159f0666520a792c1b861af4f · Note
• https://git.kernel.org/stable/c/b2c70dd3326809429b709a9c7e9220d29923051a · Note
• https://git.kernel.org/stable/c/302d57ed7872838b40e56a868fb4c7da7da606e9 · Note