Unknown

CVE-2026-64538 — ipv6: Fix null-ptr-deref in fib6_nh_mtu_change().

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 Jul 27, 2026 · Updated Oct 15, 2026 · Sources: CVE Program (cve.org) e CISA ADP, NIST National Vulnerability Database, GitHub Security Advisories · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+1

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.2%

ahead of 9% of scored CVEs · Oct 15, 2026

Affects

Linux

CVSS base

—

Score not published yet.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and < d08d019f2f43a6f9a71e81868bbc326b3afaf37b≥ c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and < 1451deca9896957159f0666520a792c1b861af4f≥ c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and < b2c70dd3326809429b709a9c7e9220d29923051a≥ c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and < 302d57ed7872838b40e56a868fb4c7da7da606e9≥ c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and < 80600b5d0f3ecb9324120dc95b5e915130f516c5≥ c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and < b0d0eb13a0441a8ebf4f227843deaf494f1e2c33≥ c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and < 6428634f7a0b7878144b4925c37856bef3224967≥ c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and < 46c3b8191aad3d032776bf3bebf03efdf5f4b905 and 1 more version 5.3	Vulnerable	CVE Program (cve.org) e CISA ADP

EPSS over time FIRST

Oct 14, 2026 → Oct 15, 2026 · 2 reading(s) · max 0.20%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Not enough vector or weakness data: use the affected application’s logs as a starting point.

application logs

Timeline

What happened to this CVE, newest first.

2026
Source status changed · Published → Received
Oct 15, 2026 · NIST National Vulnerability Database
Record published
Oct 15, 2026
Source status changed · → Published
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Record created in this database
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
CVE published
Jul 27, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

2× References added · Oct 15, 2026 – Oct 15, 2026
1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

12 on the record

github.com/advisories/GHSA-c37c-frr8-rx54
GitHub Security Advisories
git.kernel.org/stable/c/b2c70dd3326809429b709a9c7e9220d29923051a
CVE Program (cve.org) e CISA ADP
git.kernel.org/stable/c/d08d019f2f43a6f9a71e81868bbc326b3afaf37b
CVE Program (cve.org) e CISA ADP
cert-portal.siemens.com/productcert/html/ssa-457936.html
NIST National Vulnerability Database
git.kernel.org/stable/c/b0d0eb13a0441a8ebf4f227843deaf494f1e2c33
CVE Program (cve.org) e CISA ADP
git.kernel.org/stable/c/302d57ed7872838b40e56a868fb4c7da7da606e9
CVE Program (cve.org) e CISA ADP
cert-portal.siemens.com/productcert/html/ssa-019113.html
NIST National Vulnerability Database
git.kernel.org/stable/c/6428634f7a0b7878144b4925c37856bef3224967
CVE Program (cve.org) e CISA ADP
git.kernel.org/stable/c/1451deca9896957159f0666520a792c1b861af4f
CVE Program (cve.org) e CISA ADP
git.kernel.org/stable/c/46c3b8191aad3d032776bf3bebf03efdf5f4b905
CVE Program (cve.org) e CISA ADP
nvd.nist.gov/vuln/detail/CVE-2026-64538
GitHub Security Advisories
git.kernel.org/stable/c/80600b5d0f3ecb9324120dc95b5e915130f516c5
CVE Program (cve.org) e CISA ADP

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 1d
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 1d
Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 2d
Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 2d
Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 2d
Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 2d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CVSS score published by NVD, the CNA, CISA or GitHub so far.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-64538 is "ipv6: Fix null-ptr-deref in fib6_nh_mtu_change().", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.20% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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