CVE-2026-74657

ipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops

State: Published
Severity: Not scored
Published: Aug 22, 2026
Updated: Aug 27, 2026
Reserved: Aug 15, 2026

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.

Scores

The record has no CVSS score.

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	d15662682db232da77136cd348f4c9df312ca6f9 to before 57195f0ab5cfbb5ee0864e5aff15ceb48f5a5e28Affected d15662682db232da77136cd348f4c9df312ca6f9 to before 0f0ca602941d0a81ae9514943ca06c55159c6385Affected d15662682db232da77136cd348f4c9df312ca6f9 to before 5307a53599fa762c06e475ee4a375252074fd324Affected d15662682db232da77136cd348f4c9df312ca6f9 to before 7f80ad373ce4a7af5367ff273cea0f16e91387f3Affected d15662682db232da77136cd348f4c9df312ca6f9 to before 4a5dfbae5179f6574695012a980476254df2d295Affected d15662682db232da77136cd348f4c9df312ca6f9 to before a59edda6eda1252340354322d8ab318b2e9052fbAffected d15662682db232da77136cd348f4c9df312ca6f9 to before 9b22f13524fa0de0d963bbd3002df6c28bae3395Affected d15662682db232da77136cd348f4c9df312ca6f9 to before 4ff9548d84945d2cbf9e4c207288063a200ea397Affected
LinuxLinux	5.2Affected before 5.2Not affected 5.10.267 through 5.10.Not affected 5.15.216 through 5.15.Not affected 6.1.183 through 6.1.Not affected 6.6.152 through 6.6.Not affected 6.12.104 through 6.12.Not affected 6.18.45 through 6.18.Not affected 7.1.9 through 7.1.*Not affected 7.2 and laterNot affected

Product

Versions

LinuxLinux

d15662682db232da77136cd348f4c9df312ca6f9 to before 57195f0ab5cfbb5ee0864e5aff15ceb48f5a5e28Affected
d15662682db232da77136cd348f4c9df312ca6f9 to before 0f0ca602941d0a81ae9514943ca06c55159c6385Affected
d15662682db232da77136cd348f4c9df312ca6f9 to before 5307a53599fa762c06e475ee4a375252074fd324Affected
d15662682db232da77136cd348f4c9df312ca6f9 to before 7f80ad373ce4a7af5367ff273cea0f16e91387f3Affected
d15662682db232da77136cd348f4c9df312ca6f9 to before 4a5dfbae5179f6574695012a980476254df2d295Affected
d15662682db232da77136cd348f4c9df312ca6f9 to before a59edda6eda1252340354322d8ab318b2e9052fbAffected
d15662682db232da77136cd348f4c9df312ca6f9 to before 9b22f13524fa0de0d963bbd3002df6c28bae3395Affected
d15662682db232da77136cd348f4c9df312ca6f9 to before 4ff9548d84945d2cbf9e4c207288063a200ea397Affected

LinuxLinux

5.2Affected
before 5.2Not affected
5.10.267 through 5.10.*Not affected
5.15.216 through 5.15.*Not affected
6.1.183 through 6.1.*Not affected
6.6.152 through 6.6.*Not affected
6.12.104 through 6.12.*Not affected
6.18.45 through 6.18.*Not affected
7.1.9 through 7.1.*Not affected
7.2 and laterNot affected

References

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