FKIE_CVE-2026-64538
Vulnerability from fkie_nvd - Published: 2026-07-27 21:17 - Updated: 2026-07-27 21:17
Severity
Summary
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
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/ipv6/route.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "d08d019f2f43a6f9a71e81868bbc326b3afaf37b",
"status": "affected",
"version": "c0b220cf7d80eb8a36ae9f12cae6df4577a6814e",
"versionType": "git"
},
{
"lessThan": "1451deca9896957159f0666520a792c1b861af4f",
"status": "affected",
"version": "c0b220cf7d80eb8a36ae9f12cae6df4577a6814e",
"versionType": "git"
},
{
"lessThan": "b2c70dd3326809429b709a9c7e9220d29923051a",
"status": "affected",
"version": "c0b220cf7d80eb8a36ae9f12cae6df4577a6814e",
"versionType": "git"
},
{
"lessThan": "302d57ed7872838b40e56a868fb4c7da7da606e9",
"status": "affected",
"version": "c0b220cf7d80eb8a36ae9f12cae6df4577a6814e",
"versionType": "git"
},
{
"lessThan": "80600b5d0f3ecb9324120dc95b5e915130f516c5",
"status": "affected",
"version": "c0b220cf7d80eb8a36ae9f12cae6df4577a6814e",
"versionType": "git"
},
{
"lessThan": "b0d0eb13a0441a8ebf4f227843deaf494f1e2c33",
"status": "affected",
"version": "c0b220cf7d80eb8a36ae9f12cae6df4577a6814e",
"versionType": "git"
},
{
"lessThan": "6428634f7a0b7878144b4925c37856bef3224967",
"status": "affected",
"version": "c0b220cf7d80eb8a36ae9f12cae6df4577a6814e",
"versionType": "git"
},
{
"lessThan": "46c3b8191aad3d032776bf3bebf03efdf5f4b905",
"status": "affected",
"version": "c0b220cf7d80eb8a36ae9f12cae6df4577a6814e",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/ipv6/route.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "5.3"
},
{
"lessThan": "5.3",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.261",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.212",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.178",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.145",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.97",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.40",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.5",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2-rc1",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Fix null-ptr-deref in fib6_nh_mtu_change().\n\nfib6_nh_mtu_change() re-fetches idev via __in6_dev_get(arg-\u003edev) and\ndereferences idev-\u003ecnf.mtu6 without a NULL check. addrconf_ifdown()\nclears dev-\u003eip6_ptr with RCU_INIT_POINTER() after rt6_disable_ip() has\nreleased tb6_lock, so the RA-driven MTU walk can observe a NULL idev and\noops. The caller rt6_mtu_change_route() guards its own __in6_dev_get(),\nbut this re-fetch is unguarded; nexthop-backed routes survive\naddrconf_ifdown()\u0027s flush, so the walk still reaches it after ip6_ptr is\nnulled.\n\nReturn 0 when idev is NULL, matching rt6_mtu_change_route() and the\nfib6_mtu() fix in commit 5ad509c1fdad (\"ipv6: Fix null-ptr-deref in\nfib6_mtu().\").\n\n Oops: general protection fault, ... KASAN: null-ptr-deref in range\n [0x00000000000002a8-0x00000000000002af]\n RIP: 0010:fib6_nh_mtu_change+0x203/0x990\n rt6_mtu_change_route+0x141/0x1d0\n __fib6_clean_all+0xd0/0x160\n rt6_mtu_change+0xb4/0x100\n ndisc_router_discovery+0x24b5/0x2cb0\n icmpv6_rcv+0x12e9/0x1710\n ipv6_rcv+0x39b/0x410"
}
],
"id": "CVE-2026-64538",
"lastModified": "2026-07-27T21:17:06.130",
"metrics": {},
"published": "2026-07-27T21:17:06.130",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/1451deca9896957159f0666520a792c1b861af4f"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/302d57ed7872838b40e56a868fb4c7da7da606e9"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/46c3b8191aad3d032776bf3bebf03efdf5f4b905"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/6428634f7a0b7878144b4925c37856bef3224967"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/80600b5d0f3ecb9324120dc95b5e915130f516c5"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/b0d0eb13a0441a8ebf4f227843deaf494f1e2c33"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/b2c70dd3326809429b709a9c7e9220d29923051a"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/d08d019f2f43a6f9a71e81868bbc326b3afaf37b"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
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