{"id":"CVE-2026-89564","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-89564","summary":"ip: orphan prefetched skbs before multicast forwarding","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nip: orphan prefetched skbs before multicast forwarding\n\nIPv4 and IPv6 input preserve an skb->sk association installed by\nbpf_sk_assign() so that local delivery can use the selected socket under\nRCU. Both address families can also prefetch a socket in UDP early demux.\nIn both paths (BPF and UDP early demux) a reference is not guaranteed to\nbe held on the socket.\n\nWhen a multicast packet is not locally deliverable, IPv6 hands the\noriginal skb to ip6_mr_input(). IPv4's ip_mr_input() similarly keeps the\noriginal skb when local delivery is not needed. Either path can put the\nskb on an unresolved multicast route queue or forward it after the\nreceive-side RCU section ends.\n\nAfter the prefetched socket is destroyed, a later skb free invokes\nsock_pfree() and dereferences the stale skb->sk. Orphan the skb before\neach non-local multicast forwarding path. Local delivery retains the\noriginal skb; the existing skb_clone() calls provide multicast forwarding\nwith a socket-free clone.","published":"2026-09-11T19:44:35.131Z","modified":"2026-09-14T03:46:16.545042042Z","cvss":{"score":7.8,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.18.50"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/a8af6fbac895f057c4b8ff8a2e3fb4c5827fe4ce"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e36ce6e78fe3fc3c071a26750783b7ba081ce10d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f1281d4b99089fbaf0d3579bba62a814ebb4de4d"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89564.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89564"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-14T03:46:16.545042042Z"}}