CVE-2026-90037 (GCVE-0-2026-90037)

Vulnerability from cvelistv5 – Published: 2026-09-16 10:33 – Updated: 2026-10-30 12:33
VLAI
Title
NFSD: Prevent client use-after-free during close_lru reaping
Summary
In the Linux kernel, the following vulnerability has been resolved: NFSD: Prevent client use-after-free during close_lru reaping An nfs4_openowner left on nn->close_lru after its final CLOSE keeps its last closed stateid in oo_last_closed_stid, holding only a raw pointer to its nfs4_client. The laundromat reaps timed-out entries, drops nn->client_lock, and calls nfs4_put_stid(), which dereferences the client through cl_lock. Nothing pins the client across that window, so a concurrent force_expire_client() can free it and nfs4_put_stid() reads freed memory. __destroy_client() hits the same race, walking clp->cl_openowners without cl_lock. Pin the client with cl_rpc_users before dropping client_lock, and skip clients already expiring. __destroy_client() then cleans up its own close_lru entries through release_last_closed_stateid(), so teardown no longer races the laundromat.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6639 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 217526e7ecc9f6f243e976772e81eab7ab986a4c , < 1d721729762a413015864b2a56d7fb86fb8efa9f (git)
Affected: 217526e7ecc9f6f243e976772e81eab7ab986a4c , < adc34b5df5c5d87043cb500b0867fc1c4ad0117e (git)
Affected: 217526e7ecc9f6f243e976772e81eab7ab986a4c , < 0763482227822f7343557f086afc382086d56c4c (git)
Affected: 217526e7ecc9f6f243e976772e81eab7ab986a4c , < 83dd59ac1c3455c2c7d8ddb582d980a13199b9b3 (git)
Affected: 217526e7ecc9f6f243e976772e81eab7ab986a4c , < e57a9ed34ea8c17e831de59b8f1a6b2d80d347a1 (git)
Affected: 217526e7ecc9f6f243e976772e81eab7ab986a4c , < 2330b788d732f43668b965b3105b37ceb276dfea (git)
guessed Create a notification for this product.
Linux Linux Affected: 3.17
Unaffected: 0 , < 3.17 (semver)
Unaffected: 6.1.191 , ≤ 6.1.* (semver)
Unaffected: 6.6.160 , ≤ 6.6.* (semver)
Unaffected: 6.12.111 , ≤ 6.12.* (semver)
Unaffected: 6.18.51 , ≤ 6.18.* (semver)
Unaffected: 7.2.5 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Prevent client use-after-free during close_lru reaping\n\nAn nfs4_openowner left on nn-\u003eclose_lru after its final CLOSE keeps\nits last closed stateid in oo_last_closed_stid, holding only a raw\npointer to its nfs4_client. The laundromat reaps timed-out entries,\ndrops nn-\u003eclient_lock, and calls nfs4_put_stid(), which dereferences\nthe client through cl_lock. Nothing pins the client across that\nwindow, so a concurrent force_expire_client() can free it and\nnfs4_put_stid() reads freed memory. __destroy_client() hits the same\nrace, walking clp-\u003ecl_openowners without cl_lock.\n\nPin the client with cl_rpc_users before dropping client_lock, and\nskip clients already expiring. __destroy_client() then cleans up its\nown close_lru entries through release_last_closed_stateid(), so\nteardown no longer races the laundromat."
        }
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            "baseSeverity": "CRITICAL",
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            "version": "3.1"
          },
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              "value": "AV:N - nfsd is the in-kernel NFS server. A remote NFSv4.0 client reaches the UAF over TCP/UDP 2049: CLOSE places the openowner on nn-\u003eclose_lru, and SETCLIENTID_CONFIRM (ALLOWED_WITHOUT_FH) calls expire_client() while nfs4_laundromat() drops client_lock and nfs4_put_stid() uses the unpinned nfs4_client.\nAC:L - The attacker drives both sides: OPEN/CLOSE compounds fill close_lru so the laundromat drops client_lock once per nfs4_put_stid(), and concurrent SETCLIENTID_CONFIRM with matching AUTH_SYS creds replaces the client via expire_client(). FATTR4_LEASE_TIME times the window; flooding close_lru widens it; the race is retryable.\nPR:N - Typical nfsd deployments use AUTH_SYS/AUTH_NULL, so RPC uids are self-asserted. SETCLIENTID and SETCLIENTID_CONFIRM are ALLOWED_WITHOUT_FH; any host allowed by the export can OPEN/CLOSE and replace the client with no local account or capability on the NFS server.\nUI:N - The attacker issues the NFSv4.0 compounds (SETCLIENTID, OPEN, CLOSE, RENEW, SETCLIENTID_CONFIRM) itself. No administrator or other user on the victim server must mount a filesystem, write nfsdfs ctl, or otherwise interact.\nS:U - The use-after-free is of the nfsd nfs4_client object (client_slab) in the NFS server kernel. Impact stays in that kernel security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - After free_client() kmem_cache_free()s the nfs4_client, nfs4_put_stid() still reads cl_lock and cl_stateids. Reclaiming the mergeable client_slab object via further SETCLIENTID discloses kernel heap; a UAF is C:H.\nI:H - nfs4_put_stid() then takes cl_lock and idr_remove()s from cl_stateids on the freed nfs4_client, a slab UAF write concurrent with __destroy_client(). Heap reuse enables arbitrary write and control-flow hijack; a UAF is I:H.\nA:H - Use-after-free of nfs4_client in nfs4_put_stid() (spin_lock of freed cl_lock) oopses or panics the nfsd laundromat worker even without a full exploit, denying service of the NFS server host."
            }
          ]
        }
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      "providerMetadata": {
        "dateUpdated": "2026-10-30T12:33:53.924Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/adc34b5df5c5d87043cb500b0867fc1c4ad0117e"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90037",
    "datePublished": "2026-09-16T10:33:36.673Z",
    "dateReserved": "2026-09-11T19:38:34.782Z",
    "dateUpdated": "2026-10-30T12:33:53.924Z",
    "state": "PUBLISHED"
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      "cve": "CVE-2026-90037",
      "id": "msrc_CVE-2026-90037",
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      "product_status:fixed": "1",
      "product_status:known_affected": "4",
      "product_status:under_investigation": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "NFSD: Prevent client use-after-free during close_lru reaping",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-90037.json",
      "version": "8"
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                "vendor": "Linux",
                "versions": [
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            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Prevent client use-after-free during close_lru reaping\n\nAn nfs4_openowner left on nn-\u003eclose_lru after its final CLOSE keeps\nits last closed stateid in oo_last_closed_stid, holding only a raw\npointer to its nfs4_client. The laundromat reaps timed-out entries,\ndrops nn-\u003eclient_lock, and calls nfs4_put_stid(), which dereferences\nthe client through cl_lock. Nothing pins the client across that\nwindow, so a concurrent force_expire_client() can free it and\nnfs4_put_stid() reads freed memory. __destroy_client() hits the same\nrace, walking clp-\u003ecl_openowners without cl_lock.\n\nPin the client with cl_rpc_users before dropping client_lock, and\nskip clients already expiring. __destroy_client() then cleans up its\nown close_lru entries through release_last_closed_stateid(), so\nteardown no longer races the laundromat."
          }
        ],
        "id": "CVE-2026-90037",
        "lastModified": "2026-10-30T13:20:39.433",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 9.8,
                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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        "published": "2026-09-16T11:17:16.910",
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            "url": "https://git.kernel.org/stable/c/e57a9ed34ea8c17e831de59b8f1a6b2d80d347a1"
          }
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-11-06T01:28:27+00:00",
      "cve": "CVE-2026-90037",
      "id": "CVE-2026-90037",
      "initial_release_date": "2026-09-16T00:00:00+00:00",
      "product_status:known_affected": "203",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: NFSD: Prevent client use-after-free during close_lru reaping",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-90037.json",
      "version": "3"
    }
  }
}



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How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

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