CVE-2026-64538 - Vulnerability Details

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

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

Published: 2026-07-27

Score: n/a

EPSS: n/a

KEV: No

Impact:

Action:

Analysis

No analysis available yet.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Linux

unaffected

Version	Status	Constraints
`c0b220cf7d80eb8a36ae9f12cae6df4577a6814e`	affected	< d08d019f2f43a6f9a71e81868bbc326b3afaf37b
`c0b220cf7d80eb8a36ae9f12cae6df4577a6814e`	affected	< 1451deca9896957159f0666520a792c1b861af4f
`c0b220cf7d80eb8a36ae9f12cae6df4577a6814e`	affected	< b2c70dd3326809429b709a9c7e9220d29923051a
`c0b220cf7d80eb8a36ae9f12cae6df4577a6814e`	affected	< 302d57ed7872838b40e56a868fb4c7da7da606e9
`c0b220cf7d80eb8a36ae9f12cae6df4577a6814e`	affected	< 80600b5d0f3ecb9324120dc95b5e915130f516c5
`c0b220cf7d80eb8a36ae9f12cae6df4577a6814e`	affected	< b0d0eb13a0441a8ebf4f227843deaf494f1e2c33
`c0b220cf7d80eb8a36ae9f12cae6df4577a6814e`	affected	< 6428634f7a0b7878144b4925c37856bef3224967
`c0b220cf7d80eb8a36ae9f12cae6df4577a6814e`	affected	< 46c3b8191aad3d032776bf3bebf03efdf5f4b905

Linux

affected

Version	Status	Constraints
`5.3`	affected	—
`0`	unaffected	< 5.3
`5.10.261`	unaffected	≤ 5.10.*
`5.15.212`	unaffected	≤ 5.15.*
`6.1.178`	unaffected	≤ 6.1.*
`6.6.145`	unaffected	≤ 6.6.*
`6.12.97`	unaffected	≤ 6.12.*
`6.18.40`	unaffected	≤ 6.18.*
`7.1.5`	unaffected	≤ 7.1.*
`7.2-rc1`	unaffected	≤ *

No data.

No data available yet.

Remediation

No remediation available yet.

Tracking

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Advisories

No advisories yet.

No CVSS v4.0

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/stable/c/1451deca9896957159f0666520a792c1b861af4f
https://git.kernel.org/stable/c/302d57ed7872838b40e56a868fb4c7da7da606e9
https://git.kernel.org/stable/c/46c3b8191aad3d032776bf3bebf03efdf5f4b905
https://git.kernel.org/stable/c/6428634f7a0b7878144b4925c37856bef3224967
https://git.kernel.org/stable/c/80600b5d0f3ecb9324120dc95b5e915130f516c5
https://git.kernel.org/stable/c/b0d0eb13a0441a8ebf4f227843deaf494f1e2c33
https://git.kernel.org/stable/c/b2c70dd3326809429b709a9c7e9220d29923051a
https://git.kernel.org/stable/c/d08d019f2f43a6f9a71e81868bbc326b3afaf37b

History

Mon, 27 Jul 2026 20:30:00 +0000

Type	Values Removed	Values Added
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
Title		ipv6: Fix null-ptr-deref in fib6_nh_mtu_change().
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/1451deca9896957159f0666520a792c1b861af4f https://git.kernel.org/stable/c/302d57ed7872838b40e56a868fb4c7da7da606e9 https://git.kernel.org/stable/c/46c3b8191aad3d032776bf3bebf03efdf5f4b905 https://git.kernel.org/stable/c/6428634f7a0b7878144b4925c37856bef3224967 https://git.kernel.org/stable/c/80600b5d0f3ecb9324120dc95b5e915130f516c5 https://git.kernel.org/stable/c/b0d0eb13a0441a8ebf4f227843deaf494f1e2c33 https://git.kernel.org/stable/c/b2c70dd3326809429b709a9c7e9220d29923051a https://git.kernel.org/stable/c/d08d019f2f43a6f9a71e81868bbc326b3afaf37b

Subscriptions

Linux Linux Kernel

MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2026-07-27T20:10:32.779Z

Updated: 2026-07-27T20:10:32.779Z

Reserved: 2026-07-19T15:36:31.795Z

Link: CVE-2026-64538

Vulnrichment

No data.

NVD

No data.

Redhat

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OpenCVE Enrichment

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Weaknesses

No weakness.

Tracking

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