CVE-2026-64538
Full vulnerability record from the local CVENow database.
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
Severity
Not scored
CVSS score
Not available
Vulnerability status
Awaiting Analysis
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-07-27 21:17:06.130000
Last modified
2026-11-03 18:15:39.353000
View original CVE JSON
{
"id": "CVE-2026-64538",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-07-27T21:17:06.130",
"lastModified": "2026-11-03T18:15:39.353",
"vulnStatus": "Awaiting Analysis",
"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->dev) and\ndereferences idev->cnf.mtu6 without a NULL check. addrconf_ifdown()\nclears dev->ip6_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()'s 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"
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"net/ipv6/route.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
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},
{
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"programFiles": [
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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{
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{
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{
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{
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},
{
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{
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"versionType": "original_commit_for_fix",
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]
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]
},
{
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"product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
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},
{
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"metrics": {},
"references": [
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