CVE-2026-64538

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

State: Published
Severity: Not scored
Published: Jul 27, 2026
Updated: Oct 15, 2026
Reserved: Jul 19, 2026

Description

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

Scores

The record has no CVSS score.

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before d08d019f2f43a6f9a71e81868bbc326b3afaf37bAffected c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before 1451deca9896957159f0666520a792c1b861af4fAffected c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before b2c70dd3326809429b709a9c7e9220d29923051aAffected c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before 302d57ed7872838b40e56a868fb4c7da7da606e9Affected c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before 80600b5d0f3ecb9324120dc95b5e915130f516c5Affected c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before b0d0eb13a0441a8ebf4f227843deaf494f1e2c33Affected c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before 6428634f7a0b7878144b4925c37856bef3224967Affected c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before 46c3b8191aad3d032776bf3bebf03efdf5f4b905Affected
LinuxLinux	5.3Affected before 5.3Not affected 5.10.261 through 5.10.Not affected 5.15.212 through 5.15.Not affected 6.1.178 through 6.1.Not affected 6.6.145 through 6.6.Not affected 6.12.97 through 6.12.Not affected 6.18.40 through 6.18.Not affected 7.1.5 through 7.1.*Not affected 7.2 and laterNot affected

Product

Versions

LinuxLinux

c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before d08d019f2f43a6f9a71e81868bbc326b3afaf37bAffected
c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before 1451deca9896957159f0666520a792c1b861af4fAffected
c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before b2c70dd3326809429b709a9c7e9220d29923051aAffected
c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before 302d57ed7872838b40e56a868fb4c7da7da606e9Affected
c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before 80600b5d0f3ecb9324120dc95b5e915130f516c5Affected
c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before b0d0eb13a0441a8ebf4f227843deaf494f1e2c33Affected
c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before 6428634f7a0b7878144b4925c37856bef3224967Affected
c0b220cf7d80eb8a36ae9f12cae6df4577a6814e to before 46c3b8191aad3d032776bf3bebf03efdf5f4b905Affected

LinuxLinux

5.3Affected
before 5.3Not affected
5.10.261 through 5.10.*Not affected
5.15.212 through 5.15.*Not affected
6.1.178 through 6.1.*Not affected
6.6.145 through 6.6.*Not affected
6.12.97 through 6.12.*Not affected
6.18.40 through 6.18.*Not affected
7.1.5 through 7.1.*Not affected
7.2 and laterNot affected

References

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