{ "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": "2026-10-21T12:47:52.511Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-21T12:47:52.511Z" }, "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": "882212d317a7c16ab70d20656f6b1c42abada9f6", "status": "affected", "versionType": "git" }, { "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": "6.6.160", "lessThanOrEqual": "6.6.*", "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", "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": "6.6.160" }, { "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" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/882212d317a7c16ab70d20656f6b1c42abada9f6" }, { "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" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-89564", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "total" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:24:14.849445Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:26:44.346Z" } } ] } }