{"id":"CVE-2026-74657","summary":"ipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops\n\nfib_nlmsg_size() still estimates nexthop space as if every gateway is\nencoded as an IPv4 RTA_GATEWAY attribute. IPv4 routes can also carry an\nIPv6 gateway, which fib_nexthop_info() dumps as RTA_VIA.\n\nAs a result, route notifications can allocate an skb that is too small.\nfib_dump_info() then fails with -EMSGSIZE and rtmsg_fib() hits the\nWARN_ON() that marks such failures as a fib_nlmsg_size() bug. With\npanic_on_warn set, this becomes a kernel panic.\n\nMirror the actual nexthop dump layout in fib_nlmsg_size(): account for\nIPv6 nexthop gateways dumped as RTA_VIA, for the no-header rtnexthop\nlayout used inside RTA_MULTIPATH, and for RTA_FLOW only when it is\nactually present.","modified":"2026-08-24T11:47:20.420913627Z","published":"2026-08-22T15:32:31.458Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74657.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0f0ca602941d0a81ae9514943ca06c55159c6385"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4a5dfbae5179f6574695012a980476254df2d295"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4ff9548d84945d2cbf9e4c207288063a200ea397"},{"type":"WEB","url":"https://git.kernel.org/stable/c/5307a53599fa762c06e475ee4a375252074fd324"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7f80ad373ce4a7af5367ff273cea0f16e91387f3"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9b22f13524fa0de0d963bbd3002df6c28bae3395"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a59edda6eda1252340354322d8ab318b2e9052fb"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74657.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74657"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"d15662682db232da77136cd348f4c9df312ca6f9"},{"fixed":"0f0ca602941d0a81ae9514943ca06c55159c6385"},{"fixed":"5307a53599fa762c06e475ee4a375252074fd324"},{"fixed":"7f80ad373ce4a7af5367ff273cea0f16e91387f3"},{"fixed":"4a5dfbae5179f6574695012a980476254df2d295"},{"fixed":"a59edda6eda1252340354322d8ab318b2e9052fb"},{"fixed":"9b22f13524fa0de0d963bbd3002df6c28bae3395"},{"fixed":"4ff9548d84945d2cbf9e4c207288063a200ea397"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-74657.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.2.0"},{"fixed":"5.15.216"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.183"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.152"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.104"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.45"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.9"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-74657.json"}}],"schema_version":"1.9.0"}