CVE-2026-74657

Summary

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 Software

VendorProductVersion RangeStatus
LinuxLinuxd15662682db232da77136cd348f4c9df312ca6f9 < 0f0ca602941d0a81ae9514943ca06c55159c6385affected
LinuxLinuxd15662682db232da77136cd348f4c9df312ca6f9 < 5307a53599fa762c06e475ee4a375252074fd324affected
LinuxLinuxd15662682db232da77136cd348f4c9df312ca6f9 < 7f80ad373ce4a7af5367ff273cea0f16e91387f3affected
LinuxLinuxd15662682db232da77136cd348f4c9df312ca6f9 < 4a5dfbae5179f6574695012a980476254df2d295affected
LinuxLinuxd15662682db232da77136cd348f4c9df312ca6f9 < a59edda6eda1252340354322d8ab318b2e9052fbaffected
LinuxLinuxd15662682db232da77136cd348f4c9df312ca6f9 < 9b22f13524fa0de0d963bbd3002df6c28bae3395affected
LinuxLinuxd15662682db232da77136cd348f4c9df312ca6f9 < 4ff9548d84945d2cbf9e4c207288063a200ea397affected
LinuxLinux5.2affected
LinuxLinux0 < 5.2unaffected
LinuxLinux5.15.216 <= 5.15.*unaffected
LinuxLinux6.1.183 <= 6.1.*unaffected
LinuxLinux6.6.152 <= 6.6.*unaffected
LinuxLinux6.12.104 <= 6.12.*unaffected
LinuxLinux6.18.45 <= 6.18.*unaffected
LinuxLinux7.1.9 <= 7.1.*unaffected
LinuxLinux7.2 <= *unaffected

Weaknesses

References