CVE-2026-74657
In the Linux kernel, the following vulnerability has been resolved: ipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops fib_nlmsg_size() still estimates nexthop space as if every gateway is encoded as an IPv4 RTA_GATEWAY attribute. IPv4 routes can also carry an IPv6 gateway, which fib_nexthop_info() dumps as RTA_VIA. As a result, route notifications can allocate an skb that is too small. fib_dump_info() then fails with -EMSGSIZE and rtmsg_fib() hits the WARN_ON() that marks such failures as a fib_nlmsg_size() bug. With panic_on_warn set, this becomes a kernel panic. Mirror the actual nexthop dump layout in fib_nlmsg_size(): account for IPv6 nexthop gateways dumped as RTA_VIA, for the no-header rtnexthop layout used inside RTA_MULTIPATH, and for RTA_FLOW only when it is actually present.
Affected versions
Linux kernel versions
5.2
and later are affected. Fixed in
5.15.216,
6.1.183,
6.6.152,
6.12.104,
6.18.45,
7.1.9,
7.2
and their respective stable series.
References
7 totalFrequently asked questions
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What is CVE-2026-74657?
CVE-2026-74657 is a unscored severity Linux kernel vulnerability . It affects Linux kernel versions from 5.2 onward and has been patched in 5.15.216, 6.1.183, 6.6.152 and others. CVE-2026-74657 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
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Is there a patch available for CVE-2026-74657?
Yes. CVE-2026-74657 has been patched. Fixed versions include 5.15.216, 6.1.183, 6.6.152 and others. If you are running Linux kernel 5.2 or later up to the fix versions, apply the relevant patch for your kernel branch.
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Is CVE-2026-74657 actively exploited?
No. CVE-2026-74657 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.