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CVE-2026-89709 (GCVE-0-2026-89709)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:46 – Updated: 2026-09-13 06:33
VLAI
Title
lockd, nfsd: RCU-protect nlmsvc_ops dispatch
Summary
In the Linux kernel, the following vulnerability has been resolved: lockd, nfsd: RCU-protect nlmsvc_ops dispatch nlmsvc_ops is published by nfsd_lockd_init() and cleared by nfsd_lockd_shutdown() with plain stores, while lockd dereferences it unguarded from dispatch sites in fs/lockd/svcsubs.c. The pointer targets nfsd's .rodata and the fopen/fclose callbacks live in nfsd's .text, so a stale load after rmmod nfsd results in either a NULL deref or a module-text use-after-free. Declare nlmsvc_ops as __rcu, publish via rcu_assign_pointer(), clear via RCU_INIT_POINTER() + synchronize_rcu(). Add a struct module *owner field to nlmsvc_binding and pin the module across indirect calls with try_module_get/module_put. When the binding is torn down, fall back to fput() to avoid leaking struct file references.
Severity
8.1 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 3c461a1820088fb5889d73a6522369bde45527a9 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 641e5e20852359b8c31149be4598884e30652f60 (git)
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Linux Linux Affected: 2.6.12
Unaffected: 0 , < 2.6.12 (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": [
            "fs/lockd/svc.c",
            "fs/lockd/svc4proc.c",
            "fs/lockd/svcproc.c",
            "fs/lockd/svcsubs.c",
            "fs/nfsd/lockd.c",
            "include/linux/lockd/bind.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "3c461a1820088fb5889d73a6522369bde45527a9",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "641e5e20852359b8c31149be4598884e30652f60",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/lockd/svc.c",
            "fs/lockd/svc4proc.c",
            "fs/lockd/svcproc.c",
            "fs/lockd/svcsubs.c",
            "fs/nfsd/lockd.c",
            "include/linux/lockd/bind.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.12"
            },
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
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          "nodes": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                }
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nlockd, nfsd: RCU-protect nlmsvc_ops dispatch\n\nnlmsvc_ops is published by nfsd_lockd_init() and cleared by\nnfsd_lockd_shutdown() with plain stores, while lockd dereferences\nit unguarded from dispatch sites in fs/lockd/svcsubs.c. The pointer\ntargets nfsd\u0027s .rodata and the fopen/fclose callbacks live in nfsd\u0027s\n.text, so a stale load after rmmod nfsd results in either a NULL\nderef or a module-text use-after-free.\n\nDeclare nlmsvc_ops as __rcu, publish via rcu_assign_pointer(), clear\nvia RCU_INIT_POINTER() + synchronize_rcu(). Add a struct module\n*owner field to nlmsvc_binding and pin the module across indirect\ncalls with try_module_get/module_put. When the binding is torn down,\nfall back to fput() to avoid leaking struct file references."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - lockd is the in-kernel NLM RPC server on TCP/UDP (rpcbind-registered) used with nfsd. nlm_do_fopen() and nlm_delete_file() run from NLM LOCK/TEST/UNLOCK/FREE_ALL in svc_recv, so a remote NFS/NLM peer reaches the unguarded nlmsvc_ops-\u003efopen/fclose dispatch.\nAC:H - The UAF requires exit_nfsd()/rmmod nfsd to NULL nlmsvc_ops with a plain store and free nfsd .text while lockd still dispatches. A remote attacker can flood NLM requests but cannot unload nfsd; that victim-side module teardown is beyond attacker control.\nPR:N - lockd_authenticate() accepts RPC_AUTH_NULL and RPC_AUTH_UNIX before procedure dispatch. nlm_fopen() uses NFSD_MAY_BYPASS_GSS|NFSD_MAY_NLM, and typical exports use AUTH_SYS, so no host account or capability is required.\nUI:N - Exploitation is driven by attacker-sent NLM RPCs to an already-running lockd; no victim user must mount a filesystem or open a file. nfsd unload is an environmental timing condition, not User Interaction.\nS:U - The module-text UAF and NULL deref corrupt host kernel lockd/nfsd state within the same OS security authority and do not cross a VM, IOMMU, or sandbox boundary.\nC:H - After rmmod, a stale nlmsvc_ops load calls fopen/fclose from freed nfsd .rodata/.text. Reclaim of those module pages lets the attacker control the indirect-call target, yielding an arbitrary kernel read per UAF guidance.\nI:H - Indirect call through a dangling nlmsvc_binding in freed nfsd module memory is a RIP-hijack primitive; spraying recycled module pages enables arbitrary kernel write and control-flow hijack, so integrity impact is high.\nA:H - A stale nlmsvc_ops load after rmmod nfsd is either a NULL deref or a call into unmapped module text; both oops/panic the kernel, so availability impact is high."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:33:32.344Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/3c461a1820088fb5889d73a6522369bde45527a9"
        },
        {
          "url": "https://git.kernel.org/stable/c/641e5e20852359b8c31149be4598884e30652f60"
        }
      ],
      "title": "lockd, nfsd: RCU-protect nlmsvc_ops dispatch",
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        "engine": "bippy-1.2.0"
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  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89709",
    "datePublished": "2026-09-11T19:46:24.803Z",
    "dateReserved": "2026-09-11T19:38:34.751Z",
    "dateUpdated": "2026-09-13T06:33:32.344Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-89709",
      "date": "2026-09-15",
      "epss": "0.0033",
      "percentile": "0.26021"
    },
    "microsoft_vex": {
      "current_release_date": "2026-09-14T14:59:05.000Z",
      "cve": "CVE-2026-89709",
      "id": "msrc_CVE-2026-89709",
      "initial_release_date": "2026-09-13T01:11:48.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "lockd, nfsd: RCU-protect nlmsvc_ops dispatch",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-89709.json",
      "version": "2"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-89709\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-09-11T20:19:58.270\",\"lastModified\":\"2026-09-13T07:17:36.617\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nlockd, nfsd: RCU-protect nlmsvc_ops dispatch\\n\\nnlmsvc_ops is published by nfsd_lockd_init() and cleared by\\nnfsd_lockd_shutdown() with plain stores, while lockd dereferences\\nit unguarded from dispatch sites in fs/lockd/svcsubs.c. The pointer\\ntargets nfsd\u0027s .rodata and the fopen/fclose callbacks live in nfsd\u0027s\\n.text, so a stale load after rmmod nfsd results in either a NULL\\nderef or a module-text use-after-free.\\n\\nDeclare nlmsvc_ops as __rcu, publish via rcu_assign_pointer(), clear\\nvia RCU_INIT_POINTER() + synchronize_rcu(). Add a struct module\\n*owner field to nlmsvc_binding and pin the module across indirect\\ncalls with try_module_get/module_put. When the binding is torn down,\\nfall back to fput() to avoid leaking struct file references.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/lockd/svc.c\",\"fs/lockd/svc4proc.c\",\"fs/lockd/svcproc.c\",\"fs/lockd/svcsubs.c\",\"fs/nfsd/lockd.c\",\"include/linux/lockd/bind.h\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\"lessThan\":\"3c461a1820088fb5889d73a6522369bde45527a9\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\"lessThan\":\"641e5e20852359b8c31149be4598884e30652f60\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/lockd/svc.c\",\"fs/lockd/svc4proc.c\",\"fs/lockd/svcproc.c\",\"fs/lockd/svcsubs.c\",\"fs/nfsd/lockd.c\",\"include/linux/lockd/bind.h\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"2.6.12\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"2.6.12\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2.4\",\"lessThanOrEqual\":\"7.2.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.3-rc1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":8.1,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":2.2,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/3c461a1820088fb5889d73a6522369bde45527a9\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/641e5e20852359b8c31149be4598884e30652f60\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-09-13T06:52:29+00:00",
      "cve": "CVE-2026-89709",
      "id": "CVE-2026-89709",
      "initial_release_date": "2026-09-11T19:46:24.803000+00:00",
      "product_status:known_affected": "2",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: Linux kernel: lockd and nfsd denial of service vulnerability",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89709.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-12T16:23:13Z",
      "cve": "CVE-2026-89709",
      "id": "CVE-2026-89709",
      "initial_release_date": "2026-09-12T16:23:13Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89709",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-89709.json",
      "version": "2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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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.