CVE-2026-64576: nexthop: initialize extack in nh_res_bucket_migrate()

mediumCVSS 4.1CVE-2026-64576

CSIRTS triage

product: Linux kernel nexthop Denial of service

What: Missing extack initialization in nh_res_bucket_migrate() causes improper error handling leading to a denial-of-service.
Who is affected: Systems running the Linux kernel with nexthop multipath routing enabled.
Urgency: Medium severity with CVSS 4.1; should be addressed within normal update cycles.
Action: Update the Linux kernel to a version with the nexthop extack initialization fix.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 4.1
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64576

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-645760.12% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 2% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-64576	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

unknownMultiple vulnerabilities in Debian Linux kernel (August 14, 2026)cert-fr-avis
medium[UPDATE] [medium] Linux Kernel: Multiple vulnerabilitiescert-bund
unknownDSA-6415-1 linux - security updatedebian
highCVE-2026-64576: In the Linux kernel, the following vulnerability has been resolved: nexthop: initialize extack…nvd

Recent advisories for nexthop

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

unknownCVE-2026-74562: In the Linux kernel, the following vulnerability has been resolved: nexthop: take nh->lock for…nvd · 2026-08-15
unknownCVE-2026-74561: In the Linux kernel, the following vulnerability has been resolved: nexthop: avoid unlocked f6…nvd · 2026-08-15
mediumCVE-2024-14040: net: nexthop: Increase weight to u16msrc · 2026-08-06
highCVE-2026-64576: In the Linux kernel, the following vulnerability has been resolved: nexthop: initialize extack…nvd · 2026-08-05
highCVE-2024-14040: In the Linux kernel, the following vulnerability has been resolved: net: nexthop: Increase wei…nvd · 2026-07-26
mediumCVE-2026-53012: nexthop: fix IPv6 route referencing IPv4 nexthopmsrc · 2026-06-09