CVE-2026-74657
N/AIn 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.
No known exploitation, public exploit, or elevated probability at this time. Track for changes.
Exploitation likelihood
—EPSS not yet scored
Impact if exploited
—CVSS · not scored
- No impact metrics
Proof of concept & exploit code
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curl -s https://vulnpedia.com/cve/CVE-2026-74657/poc.jsonMachine-readable PoC index for this CVE (for automation).Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-74657/poc.json
References
Technical & other
- https://git.kernel.org/stable/c/0f0ca602941d0a81ae9514943ca06c55159c6385
- https://git.kernel.org/stable/c/5307a53599fa762c06e475ee4a375252074fd324
- https://git.kernel.org/stable/c/7f80ad373ce4a7af5367ff273cea0f16e91387f3
- https://git.kernel.org/stable/c/4a5dfbae5179f6574695012a980476254df2d295
- https://git.kernel.org/stable/c/a59edda6eda1252340354322d8ab318b2e9052fb
- https://git.kernel.org/stable/c/9b22f13524fa0de0d963bbd3002df6c28bae3395
- https://git.kernel.org/stable/c/4ff9548d84945d2cbf9e4c207288063a200ea397