{"id":"CVE-2024-56751","title":"ipv6: release nexthop on device removal","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: release nexthop on device removal\n\nThe CI is hitting some aperiodic hangup at device removal time in the\npmtu.sh self-test:\n\nunregister_netdevice: waiting for vet…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < 77aa9855a878fb43f547ddfbda3127a1e88ad31a","Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < b2f26a27ea3f72f75d18330f76f5d1007c791848","Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < 43e25adc80269f917d2a195f0d59f74cdd182955","Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < a3c3f8a4d025acc8c857246ec2b812c59102487a","Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < 0e4c6faaef8a24b762a24ffb767280e263ef8e10","Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < eb02688c5c45c3e7af7e71f036a7144f5639cbfe","Linux 5.3"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-05T20:32:24.098521Z"},"published":"2024-12-29","updated":"2026-11-05","sourceUpdated":"2026-11-05T20:41:37.543Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2024-56751","references":[{"url":"https://git.kernel.org/stable/c/77aa9855a878fb43f547ddfbda3127a1e88ad31a"},{"url":"https://git.kernel.org/stable/c/b2f26a27ea3f72f75d18330f76f5d1007c791848"},{"url":"https://git.kernel.org/stable/c/43e25adc80269f917d2a195f0d59f74cdd182955"},{"url":"https://git.kernel.org/stable/c/a3c3f8a4d025acc8c857246ec2b812c59102487a"},{"url":"https://git.kernel.org/stable/c/0e4c6faaef8a24b762a24ffb767280e263ef8e10"},{"url":"https://git.kernel.org/stable/c/eb02688c5c45c3e7af7e71f036a7144f5639cbfe"}],"tags":["cve.org"],"epss":0.00219,"epssPercentile":0.12484,"ingestedAt":"2026-11-05T22:38:31.843Z","slug":"CVE-2024-56751","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nipv6: release nexthop on device removal\n\nThe CI is hitting some aperiodic hangup at device removal time in the\npmtu.sh self-test:\n\nunregister_netdevice: waiting for veth_A-R1 to become free. Usage count = 6\nref_tracker: veth_A-R1@ffff888013df15d8 has 1/5 users at\n\tdst_init+0x84/0x4a0\n\tdst_alloc+0x97/0x150\n\tip6_dst_alloc+0x23/0x90\n\tip6_rt_pcpu_alloc+0x1e6/0x520\n\tip6_pol_route+0x56f/0x840\n\tfib6_rule_lookup+0x334/0x630\n\tip6_route_output_flags+0x259/0x480\n\tip6_dst_lookup_tail.constprop.0+0x5c2/0x940\n\tip6_dst_lookup_flow+0x88/0x190\n\tudp_tunnel6_dst_lookup+0x2a7/0x4c0\n\tvxlan_xmit_one+0xbde/0x4a50 [vxlan]\n\tvxlan_xmit+0x9ad/0xf20 [vxlan]\n\tdev_hard_start_xmit+0x10e/0x360\n\t__dev_queue_xmit+0xf95/0x18c0\n\tarp_solicit+0x4a2/0xe00\n\tneigh_probe+0xaa/0xf0\n\nWhile the first suspect is the dst_cache, explicitly tracking the dst\nowing the last device reference via probes proved such dst is held by\nthe nexthop in the originating fib6_info.\n\nSimilar to commit f5b51fe804ec (\"ipv6: route: purge exception on\nremoval\"), we need to explicitly release the originating fib info when\ndisconnecting a to-be-removed device from a live ipv6 dst: move the\nfib6_info cleanup into ip6_dst_ifdown().\n\nTested running:\n\n./pmtu.sh cleanup_ipv6_exception\n\nin a tight loop for more than 400 iterations with no spat, running an\nunpatched kernel  I observed a splat every ~10 iterations.\n\n## Affected\n\n- `Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < 77aa9855a878fb43f547ddfbda3127a1e88ad31a`\n- `Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < b2f26a27ea3f72f75d18330f76f5d1007c791848`\n- `Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < 43e25adc80269f917d2a195f0d59f74cdd182955`\n- `Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < a3c3f8a4d025acc8c857246ec2b812c59102487a`\n- `Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < 0e4c6faaef8a24b762a24ffb767280e263ef8e10`\n- `Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < eb02688c5c45c3e7af7e71f036a7144f5639cbfe`\n- `Linux 5.3`\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":[]}