{"id":"CVE-2023-53477","title":"ipv6: Add lwtunnel encap size of all siblings in nexthop calculation","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Add lwtunnel encap size of all siblings in nexthop calculation\n\nIn function rt6_nlmsg_size(), the length of nexthop is calculated\nby multipling the nexthop length…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < aba298b35619213ca787d08d472049627d8cd012","Linux >= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < da26369377f0b671c14692e2d65ceb38131053e1","Linux >= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < dcdddb5f490890d058ea1f194d661219e92fe88d","Linux >= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < e11e4d524eba2d3c8fdf897d7ce3853f7573bae9","Linux >= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < aa75d826c221e8d48607aef33836cf872a159cf1","Linux >= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < 4cc59f386991ec9374cb4bc83dbe1c0b5a95033f","Linux 4.11"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-05T20:21:59.010628Z"},"published":"2025-10-01","updated":"2026-11-05","sourceUpdated":"2026-11-05T20:31:11.115Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2023-53477","references":[{"url":"https://git.kernel.org/stable/c/aba298b35619213ca787d08d472049627d8cd012"},{"url":"https://git.kernel.org/stable/c/da26369377f0b671c14692e2d65ceb38131053e1"},{"url":"https://git.kernel.org/stable/c/dcdddb5f490890d058ea1f194d661219e92fe88d"},{"url":"https://git.kernel.org/stable/c/e11e4d524eba2d3c8fdf897d7ce3853f7573bae9"},{"url":"https://git.kernel.org/stable/c/aa75d826c221e8d48607aef33836cf872a159cf1"},{"url":"https://git.kernel.org/stable/c/4cc59f386991ec9374cb4bc83dbe1c0b5a95033f"}],"tags":["cve.org"],"epss":0.0016,"epssPercentile":0.05153,"ingestedAt":"2026-11-05T22:38:31.800Z","slug":"CVE-2023-53477","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Add lwtunnel encap size of all siblings in nexthop calculation\n\nIn function rt6_nlmsg_size(), the length of nexthop is calculated\nby multipling the nexthop length of fib6_info and the number of\nsiblings. However if the fib6_info has no lwtunnel but the siblings\nhave lwtunnels, the nexthop length is less than it should be, and\nit will trigger a warning in inet6_rt_notify() as follows:\n\nWARNING: CPU: 0 PID: 6082 at net/ipv6/route.c:6180 inet6_rt_notify+0x120/0x130\n......\nCall Trace:\n <TASK>\n fib6_add_rt2node+0x685/0xa30\n fib6_add+0x96/0x1b0\n ip6_route_add+0x50/0xd0\n inet6_rtm_newroute+0x97/0xa0\n rtnetlink_rcv_msg+0x156/0x3d0\n netlink_rcv_skb+0x5a/0x110\n netlink_unicast+0x246/0x350\n netlink_sendmsg+0x250/0x4c0\n sock_sendmsg+0x66/0x70\n ___sys_sendmsg+0x7c/0xd0\n __sys_sendmsg+0x5d/0xb0\n do_syscall_64+0x3f/0x90\n entry_SYSCALL_64_after_hwframe+0x72/0xdc\n\nThis bug can be reproduced by script:\n\nip -6 addr add 2002::2/64 dev ens2\nip -6 route add 100::/64 via 2002::1 dev ens2 metric 100\n\nfor i in 10 20 30 40 50 60 70;\ndo\n\tip link add link ens2 name ipv_$i type ipvlan\n\tip -6 addr add 2002::$i/64 dev ipv_$i\n\tifconfig ipv_$i up\ndone\n\nfor i in 10 20 30 40 50 60;\ndo\n\tip -6 route append 100::/64 encap ip6 dst 2002::$i via 2002::1\ndev ipv_$i metric 100\ndone\n\nip -6 route append 100::/64 via 2002::1 dev ipv_70 metric 100\n\nThis patch fixes it by adding nexthop_len of every siblings using\nrt6_nh_nlmsg_size().\n\n## Affected\n\n- `Linux >= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < aba298b35619213ca787d08d472049627d8cd012`\n- `Linux >= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < da26369377f0b671c14692e2d65ceb38131053e1`\n- `Linux >= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < dcdddb5f490890d058ea1f194d661219e92fe88d`\n- `Linux >= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < e11e4d524eba2d3c8fdf897d7ce3853f7573bae9`\n- `Linux >= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < aa75d826c221e8d48607aef33836cf872a159cf1`\n- `Linux >= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < 4cc59f386991ec9374cb4bc83dbe1c0b5a95033f`\n- `Linux 4.11`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}