CVE-2026-74657: ipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops

mediumCVSS 4.4CVE-2026-74657

CSIRTS triage

vendor: Linux product: Linux kernel Information disclosure

What: Incorrect buffer size calculation in fib_nlmsg_size() for RTA_VIA nexthops leaks kernel memory.
Who is affected: Systems running Linux kernel with IPv4 routing and RTA_VIA nexthop configuration.
Urgency: Medium severity (CVSS 4.4) information disclosure; not currently exploited.
Action: Update to patched Linux kernel version containing the fib_nlmsg_size RTA_VIA 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 4.4
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-74657

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-2026-746570.17% 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-2026-74657	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

unknownCVE-2026-74657: In the Linux kernel, the following vulnerability has been resolved: ipv4: Fix fib_nlmsg_size()…nvd

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