{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89564","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-11T19:38:34.725Z","datePublished":"2026-09-11T19:44:35.131Z","dateUpdated":"2026-09-21T13:14:30.504Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-21T13:14:30.504Z"},"descriptions":[{"lang":"en","value":"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."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The UAF requires the attacker to attach a no-ref skb->sk (UDP early demux or bpf_sk_assign) and destroy that socket while the skb sits on the mroute unresolved queue; a remote multicast datagram does not prefetch onto non-local ip_mr_input/ip6_mr_input (mcast early demux needs membership, which clones; ip_forward drops skb->sk).\nAC:L - The attacker owns every step: enable mroute, bind/connect a UDP socket or attach TC bpf_sk_assign, inject a non-local multicast skb so ipmr_cache_unresolved() queues it for 10s, then close the socket and wait for kfree_skb; no uncontrolled race or memory layout is required.\nPR:L - MRT_INIT needs a raw IGMP/ICMPv6 socket (ns_capable CAP_NET_RAW) and VIFs/TC bpf_sk_assign need CAP_NET_ADMIN in the netns; an unprivileged user obtains both via unshare -Urn and never needs real init-namespace root.\nUI:N - The attacker performs the entire setup, packet injection, and socket close in their own user/net namespace; no other user must mount, open a file, or otherwise interact.\nS:U - The sock_pfree use-after-free corrupts kernel memory in the same host networking authority and does not cross a VM, IOMMU, or other security boundary.\nC:H - sock_pfree() dereferences the stale skb->sk after the SOCK_RCU_FREE socket is destroyed; that UAF on a struct sock can be reclaimed with attacker-controlled objects, yielding an arbitrary read primitive.\nI:H - If the reused object looks refcounted, sock_pfree() calls sock_gen_put() and refcount_dec_and_test() on the freed sock, giving a UAF write/control-flow hijack primitive via heap spray.\nA:H - Freeing the queued skb after socket destruction oopses in sock_pfree() even without a full exploit, so the bug is a reliable kernel crash as well as a UAF."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/ipmr.c","net/ipv6/ip6_input.c"],"versions":[{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","lessThan":"e62aef7d6a5b27569bf540bbe11a9482117ff588","status":"affected","versionType":"git"},{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","lessThan":"a8af6fbac895f057c4b8ff8a2e3fb4c5827fe4ce","status":"affected","versionType":"git"},{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","lessThan":"f1281d4b99089fbaf0d3579bba62a814ebb4de4d","status":"affected","versionType":"git"},{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","lessThan":"e36ce6e78fe3fc3c071a26750783b7ba081ce10d","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/ipmr.c","net/ipv6/ip6_input.c"],"versions":[{"version":"5.7","status":"affected"},{"version":"0","lessThan":"5.7","status":"unaffected","versionType":"semver"},{"version":"6.12.111","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.50","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.4","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3-rc1","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"6.12.111"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"6.18.50"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"7.3-rc1"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/e62aef7d6a5b27569bf540bbe11a9482117ff588"},{"url":"https://git.kernel.org/stable/c/a8af6fbac895f057c4b8ff8a2e3fb4c5827fe4ce"},{"url":"https://git.kernel.org/stable/c/f1281d4b99089fbaf0d3579bba62a814ebb4de4d"},{"url":"https://git.kernel.org/stable/c/e36ce6e78fe3fc3c071a26750783b7ba081ce10d"}],"title":"ip: orphan prefetched skbs before multicast forwarding","x_generator":{"engine":"bippy-1.2.0"}}}}