Vulnerability-Lookup

GHSA-94M9-VXGJ-4QQ7

Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-13 09:32

Details

In the Linux kernel, the following vulnerability has been resolved:

ip: orphan prefetched skbs before multicast forwarding

IPv4 and IPv6 input preserve an skb->sk association installed by bpf_sk_assign() so that local delivery can use the selected socket under RCU. Both address families can also prefetch a socket in UDP early demux. In both paths (BPF and UDP early demux) a reference is not guaranteed to be held on the socket.

When a multicast packet is not locally deliverable, IPv6 hands the original skb to ip6_mr_input(). IPv4's ip_mr_input() similarly keeps the original skb when local delivery is not needed. Either path can put the skb on an unresolved multicast route queue or forward it after the receive-side RCU section ends.

After the prefetched socket is destroyed, a later skb free invokes sock_pfree() and dereferences the stale skb->sk. Orphan the skb before each non-local multicast forwarding path. Local delivery retains the original skb; the existing skb_clone() calls provide multicast forwarding with a socket-free clone.

Severity

7.8 (High)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-89564"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-11T20:19:40Z",
    "severity": "HIGH"
  },
  "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-\u003esk 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\u0027s 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-\u003esk. 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.",
  "id": "GHSA-94m9-vxgj-4qq7",
  "modified": "2026-09-13T09:32:18Z",
  "published": "2026-09-11T21:31:32Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89564"
    },
    {
      "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"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-89564 (GCVE-0-2026-89564)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:44 – Updated: 2026-09-13 06:31

Title

ip: orphan prefetched skbs before multicast forwarding

Summary

In the Linux kernel, the following vulnerability has been resolved: ip: orphan prefetched skbs before multicast forwarding IPv4 and IPv6 input preserve an skb->sk association installed by bpf_sk_assign() so that local delivery can use the selected socket under RCU. Both address families can also prefetch a socket in UDP early demux. In both paths (BPF and UDP early demux) a reference is not guaranteed to be held on the socket. When a multicast packet is not locally deliverable, IPv6 hands the original skb to ip6_mr_input(). IPv4's ip_mr_input() similarly keeps the original skb when local delivery is not needed. Either path can put the skb on an unresolved multicast route queue or forward it after the receive-side RCU section ends. After the prefetched socket is destroyed, a later skb free invokes sock_pfree() and dereferences the stale skb->sk. Orphan the skb before each non-local multicast forwarding path. Local delivery retains the original skb; the existing skb_clone() calls provide multicast forwarding with a socket-free clone.

Severity

7.8 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

3 references

URL	Tags
https://git.kernel.org/stable/c/a8af6fbac895f057c…
https://git.kernel.org/stable/c/f1281d4b99089fbaf…
https://git.kernel.org/stable/c/e36ce6e78fe3fc3c0…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449 , < a8af6fbac895f057c4b8ff8a2e3fb4c5827fe4ce (git) Affected: cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449 , < f1281d4b99089fbaf0d3579bba62a814ebb4de4d (git) Affected: cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449 , < e36ce6e78fe3fc3c071a26750783b7ba081ce10d (git)
Linux	Linux	Affected: 5.7 Unaffected: 0 , < 5.7 (semver) Unaffected: 6.18.50 , ≤ 6.18.* (semver) Unaffected: 7.2.4 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/ipmr.c",
            "net/ipv6/ip6_input.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "a8af6fbac895f057c4b8ff8a2e3fb4c5827fe4ce",
              "status": "affected",
              "version": "cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449",
              "versionType": "git"
            },
            {
              "lessThan": "f1281d4b99089fbaf0d3579bba62a814ebb4de4d",
              "status": "affected",
              "version": "cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449",
              "versionType": "git"
            },
            {
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              "status": "affected",
              "version": "cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449",
              "versionType": "git"
            }
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        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
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            "net/ipv4/ipmr.c",
            "net/ipv6/ip6_input.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.7"
            },
            {
              "lessThan": "5.7",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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-\u003esk 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\u0027s 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-\u003esk. 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": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The UAF requires the attacker to attach a no-ref skb-\u003esk (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-\u003esk).\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-\u003esk 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."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:31:05.172Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "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"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89564",
    "datePublished": "2026-09-11T19:44:35.131Z",
    "dateReserved": "2026-09-11T19:38:34.725Z",
    "dateUpdated": "2026-09-13T06:31:05.172Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.