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NVD / CVE Program· CNA Linux

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

Noroxi assessment

Priority: Monitor (action score 0/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.20% (FIRST EPSS).
  • Fixed version: Linux Linux 1451deca9896957159f0666520a792c1b861af4f, 302d57ed7872838b40e56a868fb4c7da7da606e9, 46c3b8191aad3d032776bf3bebf03efdf5f4b905.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 1451deca9896957159f0666520a792c1b861af4f, 302d57ed7872838b40e56a868fb4c7da7da606e9, 46c3b8191aad3d032776bf3bebf03efdf5f4b905 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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

—No exploit Fix available
Published
Jul 27, 2026
Updated
Oct 15, 2026
EPSS
0.2% · 9th percentile
CWE
—

Report tools

JSON

Action score

0

Monitor

Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 5.3affected
    • c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and later · before d08d019f2f43a6f9a71e81868bbc326b3afaf37baffected · git
    • c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and later · before 1451deca9896957159f0666520a792c1b861af4faffected · git
    • c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and later · before b2c70dd3326809429b709a9c7e9220d29923051aaffected · git
    • c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and later · before 302d57ed7872838b40e56a868fb4c7da7da606e9affected · git
    • c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and later · before 80600b5d0f3ecb9324120dc95b5e915130f516c5affected · git
    • c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and later · before b0d0eb13a0441a8ebf4f227843deaf494f1e2c33affected · git
    • c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and later · before 6428634f7a0b7878144b4925c37856bef3224967affected · git
    • c0b220cf7d80eb8a36ae9f12cae6df4577a6814e and later · before 46c3b8191aad3d032776bf3bebf03efdf5f4b905affected · git
    • before 5.3not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.180-16.1.180-1
Debian:12linux-6.12before 6.12.100-1~deb12u16.12.100-1~deb12u1
Debian:13linuxbefore 6.12.100-16.12.100-1
Debian:14linuxbefore 7.1.5-17.1.5-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-64553Jul 27, 2026 · net: psample: fix info leak in PSAMPLE_ATTR_DATA
    0Monitor
  • ← EarlierCVE-2026-64555Jul 27, 2026 · KVM: arm64: nv: Fix SPSR_EL2 restore in kvm_hyp_handle_mops()
    35Monitor
  • Later →CVE-2026-64539Jul 27, 2026 · Bluetooth: eir: Fix stack OOB write when prepending the Flags AD
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux1451deca9896957159f0666520a792c1b861af4fVendor (CNA)
Linux Linux302d57ed7872838b40e56a868fb4c7da7da606e9Vendor (CNA)
Linux Linux46c3b8191aad3d032776bf3bebf03efdf5f4b905Vendor (CNA)
Linux Linux6428634f7a0b7878144b4925c37856bef3224967Vendor (CNA)
Linux Linux80600b5d0f3ecb9324120dc95b5e915130f516c5Vendor (CNA)
Linux Linuxb0d0eb13a0441a8ebf4f227843deaf494f1e2c33Vendor (CNA)
Linux Linuxb2c70dd3326809429b709a9c7e9220d29923051aVendor (CNA)
Linux Linuxd08d019f2f43a6f9a71e81868bbc326b3afaf37bVendor (CNA)
debian:linux6.1.180-1 · Debian:12Package registry (OSV)
debian:linux-6.126.12.100-1~deb12u1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (9 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records