CVE-2026-74656: ipv4: fix use-after-free in fib_nhc_update_mtu()

mediumCVSS 4.1CVE-2026-74656

CSIRTS triage

vendor: Linux product: Linux kernel Memory corruption

What: Use-after-free vulnerability in fib_nhc_update_mtu() IPv4 routing function.
Who is affected: Systems running Linux kernel with IPv4 routing enabled.
Urgency: Medium severity (CVSS 4.1) use-after-free; not currently exploited but could lead to kernel crashes or privilege escalation.
Action: Update to patched Linux kernel version containing the fib_nhc_update_mtu 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-2026-74656

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-2026-746560.18% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 7% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-74656	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

highCVE-2026-74656: In the Linux kernel, the following vulnerability has been resolved: ipv4: fix use-after-free i…nvd

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