CVE-2026-74657
Description
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.
How to fix
- Linux Linux57195f0ab5cfbb5ee0864e5aff15ceb48f5a5e28, 0f0ca602941d0a81ae9514943ca06c55159c6385, 5307a53599fa762c06e475ee4a375252074fd324, 7f80ad373ce4a7af5367ff273cea0f16e91387f3, 4a5dfbae5179f6574695012a980476254df2d295, a59edda6eda1252340354322d8ab318b2e9052fb, 9b22f13524fa0de0d963bbd3002df6c28bae3395, 4ff9548d84945d2cbf9e4c207288063a200ea397 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Linux Linux | d15662682db232da77136cd348f4c9df312ca6f9 ≤ v < 57195f0ab5cfbb5ee0864e5aff15ceb48f5a5e28, d15662682db232da77136cd348f4c9df312ca6f9 ≤ v < 0f0ca602941d0a81ae9514943ca06c55159c6385, d15662682db232da77136cd348f4c9df312ca6f9 ≤ v < 5307a53599fa762c06e475ee4a375252074fd324, d15662682db232da77136cd348f4c9df312ca6f9 ≤ v < 7f80ad373ce4a7af5367ff273cea0f16e91387f3, d15662682db232da77136cd348f4c9df312ca6f9 ≤ v < 4a5dfbae5179f6574695012a980476254df2d295, d15662682db232da77136cd348f4c9df312ca6f9 ≤ v < a59edda6eda1252340354322d8ab318b2e9052fb, d15662682db232da77136cd348f4c9df312ca6f9 ≤ v < 9b22f13524fa0de0d963bbd3002df6c28bae3395, d15662682db232da77136cd348f4c9df312ca6f9 ≤ v < 4ff9548d84945d2cbf9e4c207288063a200ea397, 5.2 | 57195f0ab5cfbb5ee0864e5aff15ceb48f5a5e28, 0f0ca602941d0a81ae9514943ca06c55159c6385, 5307a53599fa762c06e475ee4a375252074fd324, 7f80ad373ce4a7af5367ff273cea0f16e91387f3, 4a5dfbae5179f6574695012a980476254df2d295, a59edda6eda1252340354322d8ab318b2e9052fb, 9b22f13524fa0de0d963bbd3002df6c28bae3395, 4ff9548d84945d2cbf9e4c207288063a200ea397 |
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