{"id":"CVE-2026-53012","summary":"nexthop: fix IPv6 route referencing IPv4 nexthop","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnexthop: fix IPv6 route referencing IPv4 nexthop\n\nsyzbot reported a panic [1] [2].\n\nWhen an IPv6 nexthop is replaced with an IPv4 nexthop, the has_v4 flag\nof all groups containing this nexthop is not updated. This is because\nnh_group_v4_update is only called when replacing AF_INET to AF_INET6,\nbut the reverse direction (AF_INET6 to AF_INET) is missed.\n\nThis allows a stale has_v4=false to bypass fib6_check_nexthop, causing\nIPv6 routes to be attached to groups that effectively contain only AF_INET\nmembers. Subsequent route lookups then call nexthop_fib6_nh() which\nreturns NULL for the AF_INET member, leading to a NULL pointer\ndereference.\n\nFix by calling nh_group_v4_update whenever the family changes, not just\nAF_INET to AF_INET6.\n\nReproducer:\n\t# AF_INET6 blackhole\n\tip -6 nexthop add id 1 blackhole\n\t# group with has_v4=false\n\tip nexthop add id 100 group 1\n\t# replace with AF_INET (no -6), has_v4 stays false\n\tip nexthop replace id 1 blackhole\n\t# pass stale has_v4 check\n\tip -6 route add 2001:db8::/64 nhid 100\n\t# panic\n\tping -6 2001:db8::1\n\n[1] https://syzkaller.appspot.com/bug?id=e17283eb2f8dcf3dd9b47fe6f67a95f71faadad0\n[2] https://syzkaller.appspot.com/bug?id=8699b6ae54c9f35837d925686208402949e12ef3","modified":"2026-07-16T03:32:43.155209273Z","published":"2026-06-24T16:29:22.973Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53012.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/29c95185ba32b621fbc3800fb86e7dc3edf5c2be"},{"type":"WEB","url":"https://git.kernel.org/stable/c/613c8f4a501421dd258b07ea614205d4e16ec845"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6275796f22bb382f3e9aa58ed0b4ef7bdad78cb8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9c2d6770a5f4545a307eb66979bef7656a34d621"},{"type":"WEB","url":"https://git.kernel.org/stable/c/aaac3bed034239e1d75732211d9b05f30b0b4f35"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ad85961004fd4bd2f31209ac4b07612c6cefb9e7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b3b7e850e1541f0520c4a12ec884255c30427ff6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ceffe81a0be92afc0cd1340bc8ca46559cce9bb4"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53012.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53012"},{"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":"7bf4796dd09984ad1612877a82d0d139c70ae27f"},{"fixed":"ceffe81a0be92afc0cd1340bc8ca46559cce9bb4"},{"fixed":"9c2d6770a5f4545a307eb66979bef7656a34d621"},{"fixed":"6275796f22bb382f3e9aa58ed0b4ef7bdad78cb8"},{"fixed":"aaac3bed034239e1d75732211d9b05f30b0b4f35"},{"fixed":"ad85961004fd4bd2f31209ac4b07612c6cefb9e7"},{"fixed":"613c8f4a501421dd258b07ea614205d4e16ec845"},{"fixed":"b3b7e850e1541f0520c4a12ec884255c30427ff6"},{"fixed":"29c95185ba32b621fbc3800fb86e7dc3edf5c2be"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-53012.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.3.0"},{"fixed":"5.10.258"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.209"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.175"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.141"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.91"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.33"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.10"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-53012.json"}}],"schema_version":"1.7.5"}