CVE-2026-90111 (GCVE-0-2026-90111)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:06 – Updated: 2026-09-18 17:53
VLAI
Title
ip6mr: do not clone dst in ip6mr_cache_report()
Summary
In the Linux kernel, the following vulnerability has been resolved: ip6mr: do not clone dst in ip6mr_cache_report() IPv6 input attaches a non-refcounted (NOREF) dst to skbs under RCU. When an ingress multicast packet misses MFC lookup, ip6mr_cache_unresolved() places the skb onto the unresolved queue, escaping the receive-side RCU grace period. If the underlying route is deleted and freed, and the MFC queue is later resolved with a wrong parent interface, ip6_mr_forward() invokes ip6mr_cache_report(..., MRT6MSG_WRONGMIF), which executes dst_clone(skb_dst(pkt)) on the freed dst entry, triggering a slab use-after-free. Report packets queued to mroute6_sk (a raw socket) and netlink notifications do not require an attached dst entry. Fix this by: 1. Removing dst_clone() in ip6mr_cache_report() and ensuring report skbs do not hold a dst. 2. Dropping skb_dst before queuing unresolved skbs in ip6mr_cache_unresolved(), matching the fact that multicast forwarding resolves outgoing routes anew via ip6_route_output().
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 67f415dd29063a5906c560051c00e42dcf01a4dd , < 4a674afaae4136c71943aa3e35d433676fd40e8f (git)
Affected: 67f415dd29063a5906c560051c00e42dcf01a4dd , < 235b42b5860189eb8c27c36435ad932cae65a734 (git)
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Linux Linux Affected: 5.3
Unaffected: 0 , < 5.3 (semver)
Unaffected: 7.2.6 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/ip6mr.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
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              "status": "affected",
              "version": "67f415dd29063a5906c560051c00e42dcf01a4dd",
              "versionType": "git"
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          "product": "Linux",
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          "vendor": "Linux",
          "versions": [
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      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.6",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nip6mr: do not clone dst in ip6mr_cache_report()\n\nIPv6 input attaches a non-refcounted (NOREF) dst to skbs under RCU.\nWhen an ingress multicast packet misses MFC lookup,\nip6mr_cache_unresolved() places the skb onto the unresolved queue,\nescaping the receive-side RCU grace period.\n\nIf the underlying route is deleted and freed, and the MFC queue is later\nresolved with a wrong parent interface, ip6_mr_forward() invokes\nip6mr_cache_report(..., MRT6MSG_WRONGMIF), which executes\ndst_clone(skb_dst(pkt)) on the freed dst entry, triggering a slab\nuse-after-free.\n\nReport packets queued to mroute6_sk (a raw socket) and netlink\nnotifications do not require an attached dst entry.\n\nFix this by:\n1. Removing dst_clone() in ip6mr_cache_report() and ensuring report skbs\n   do not hold a dst.\n2. Dropping skb_dst before queuing unresolved skbs in\n   ip6mr_cache_unresolved(), matching the fact that multicast\n   forwarding resolves outgoing routes anew via ip6_route_output()."
        }
      ],
      "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 is dst_clone(skb_dst(pkt)) in ip6mr_cache_report(MRT6MSG_WRONGMIF) on a NOREF dst that ip6_route_input() attached and ip6mr_cache_unresolved() queued past RCU. Completing it requires deleting that fib6 route and MRT6_ADD_MFC with mf6cc_parent != the arrival vif; those are local setsockopt/netlink from the same attacker, not a field in the IPv6 multicast datagram.\nAC:L - The attacker owns every step: MRT6_INIT/ADD_MIF/ASSERT, inject a non-link-local IPv6 multicast skb so ip6_mr_input() misses the MFC and ip6mr_cache_unresolved() queues it, delete the fib6 route and wait an RCU grace period, then MRT6_ADD_MFC with the wrong parent so ip6_mr_forward() takes the WRONGMIF path.\nPR:L - inet6_create() allows SOCK_RAW/IPPROTO_ICMPV6 only with ns_capable(CAP_NET_RAW); ip6_mroute_setsockopt() then lets that mroute socket (or ns_capable(CAP_NET_ADMIN)) run MRT6_ADD_MIF, MRT6_ASSERT, and MRT6_ADD_MFC. An unprivileged user obtains both capabilities in a user+net namespace via unshare -Urn.\nUI:N - The attacker opens the raw ICMPv6 mroute socket, adds MIFs, injects the multicast skb onto a veth, deletes the fib6 route, and installs the mismatched-parent MFC entirely with their own syscalls; no other user must mount a volume or otherwise interact.\nS:U - dst_clone()/dst_hold() touch the host kernel\u0027s struct dst_entry from the IPv6 fib looked up for the queued skb; the use-after-free stays in that networking authority and does not cross a VM, IOMMU, or other boundary.\nC:H - After the fib6 route is freed, ip6mr_cache_report() still does dst_clone(skb_dst(pkt)) and dst_hold() reads __rcuref on the dangling dst_entry; that slab UAF can be reclaimed with attacker-controlled objects and used as an arbitrary kernel read.\nI:H - dst_hold() calls rcuref_get(\u0026dst-\u003e__rcuref) on the freed dst_entry, writing a reclaimable slab object that can be sprayed to forge a refcount/control-flow hijack when the WRONGMIF report clones the stale dst.\nA:H - ip6_mr_forward() invoking ip6mr_cache_report(MRT6MSG_WRONGMIF) oopses in dst_hold()/rcuref_get() on the already-freed dst_entry even without a full exploit, so the bug is a reliable kernel crash as well as a UAF."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-18T17:53:06.232Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/4a674afaae4136c71943aa3e35d433676fd40e8f"
        },
        {
          "url": "https://git.kernel.org/stable/c/235b42b5860189eb8c27c36435ad932cae65a734"
        }
      ],
      "title": "ip6mr: do not clone dst in ip6mr_cache_report()",
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        "engine": "bippy-1.2.0"
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90111",
    "datePublished": "2026-09-17T16:06:18.779Z",
    "dateReserved": "2026-09-11T19:38:34.787Z",
    "dateUpdated": "2026-09-18T17:53:06.232Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-90111",
      "date": "2026-09-25",
      "epss": "0.00165",
      "percentile": "0.05058"
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    "nvd": {
      "cve": {
        "affected": [
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                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "net/ipv6/ip6mr.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
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                    "versionType": "git"
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                "defaultStatus": "affected",
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                "programFiles": [
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                ],
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                "vendor": "Linux",
                "versions": [
                  {
                    "status": "affected",
                    "version": "5.3"
                  },
                  {
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                    "version": "0",
                    "versionType": "semver"
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                    "version": "7.2.6",
                    "versionType": "semver"
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                  }
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              }
            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nip6mr: do not clone dst in ip6mr_cache_report()\n\nIPv6 input attaches a non-refcounted (NOREF) dst to skbs under RCU.\nWhen an ingress multicast packet misses MFC lookup,\nip6mr_cache_unresolved() places the skb onto the unresolved queue,\nescaping the receive-side RCU grace period.\n\nIf the underlying route is deleted and freed, and the MFC queue is later\nresolved with a wrong parent interface, ip6_mr_forward() invokes\nip6mr_cache_report(..., MRT6MSG_WRONGMIF), which executes\ndst_clone(skb_dst(pkt)) on the freed dst entry, triggering a slab\nuse-after-free.\n\nReport packets queued to mroute6_sk (a raw socket) and netlink\nnotifications do not require an attached dst entry.\n\nFix this by:\n1. Removing dst_clone() in ip6mr_cache_report() and ensuring report skbs\n   do not hold a dst.\n2. Dropping skb_dst before queuing unresolved skbs in\n   ip6mr_cache_unresolved(), matching the fact that multicast\n   forwarding resolves outgoing routes anew via ip6_route_output()."
          }
        ],
        "id": "CVE-2026-90111",
        "lastModified": "2026-09-18T18:17:42.500",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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        "published": "2026-09-17T17:17:03.130",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/235b42b5860189eb8c27c36435ad932cae65a734"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/4a674afaae4136c71943aa3e35d433676fd40e8f"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}



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