CVE-2026-31717 (GCVE-0-2026-31717)
Vulnerability from cvelistv5
Published
2026-05-01 13:56
Modified
2026-08-05 12:24
Severity ?
8.8 (High) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate owner of durable handle on reconnect Currently, ksmbd does not verify if the user attempting to reconnect to a durable handle is the same user who originally opened the file. This allows any authenticated user to hijack an orphaned durable handle by predicting or brute-forcing the persistent ID. According to MS-SMB2, the server MUST verify that the SecurityContext of the reconnect request matches the SecurityContext associated with the existing open. Add a durable_owner structure to ksmbd_file to store the original opener's UID, GID, and account name. and catpure the owner information when a file handle becomes orphaned. and implementing ksmbd_vfs_compare_durable_owner() to validate the identity of the requester during SMB2_CREATE (DHnC).
References
Impacted products
Vendor Product Version
Linux Linux Version: 8df4bcdb0a4232192b2445256c39b787d58ef14d
Version: c8efcc786146a951091588e5fa7e3c754850cb3c
Version: c8efcc786146a951091588e5fa7e3c754850cb3c
Version: c8efcc786146a951091588e5fa7e3c754850cb3c
Version: c8efcc786146a951091588e5fa7e3c754850cb3c
Version: 6.6.32   ≤
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{
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            "fs/smb/server/smb2pdu.c",
            "fs/smb/server/vfs_cache.c",
            "fs/smb/server/vfs_cache.h"
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      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: validate owner of durable handle on reconnect\n\nCurrently, ksmbd does not verify if the user attempting to reconnect\nto a durable handle is the same user who originally opened the file.\nThis allows any authenticated user to hijack an orphaned durable handle\nby predicting or brute-forcing the persistent ID.\n\nAccording to MS-SMB2, the server MUST verify that the SecurityContext\nof the reconnect request matches the SecurityContext associated with\nthe existing open.\nAdd a durable_owner structure to ksmbd_file to store the original opener\u0027s\nUID, GID, and account name. and catpure the owner information when a file\nhandle becomes orphaned. and implementing ksmbd_vfs_compare_durable_owner()\nto validate the identity of the requester during SMB2_CREATE (DHnC)."
        }
      ],
      "metrics": [
        {
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
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              "value": "AV:N - ksmbd is an in-kernel SMB server reachable over the network via SMB requests, including SMB2 CREATE durable-handle reconnects.\nAC:L - Exploitation does not require a race or conditions outside attacker control; an attacker can send reconnect requests and predict or brute-force the global persistent ID in a reasonable multi-user durable-handle deployment.\nPR:L - The SMB2 CREATE path requires a valid authenticated session and tree connection before reaching the vulnerable durable reconnect logic. The flaw allows any authenticated SMB user to hijack another user\u0027s orphaned durable handle.\nUI:N - No victim interaction is required at exploit time; the attacker sends network SMB requests directly to the server.\nS:U - The impact remains within the ksmbd/file-server security authority and does not cross a VM, sandbox, or hardware isolation boundary.\nC:H - A hijacked durable handle can be used to read victim-opened files using the original handle\u0027s access rights, bypassing normal open-time ACL checks. This can expose full contents of sensitive files.\nI:H - The reconnected handle reuses the original `fp-\u003edaccess`, so if the victim handle had write, set-info, rename, truncate, or delete rights, the attacker can modify victim data with those rights.\nA:H - The attacker can steal or close the durable handle and, when the original handle carries write/delete/truncate rights, render victim data or critical shared files unavailable."
            }
          ]
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      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:24:48.598Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/712cdf917e77a6444ce3836874829d770db20ee6"
        },
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          "url": "https://git.kernel.org/stable/c/c7f0f0d01c88bdcb8b1694d7d321670013f7ed7d"
        },
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          "url": "https://git.kernel.org/stable/c/c908c853f304a4969b5aa10eba0b50350cc65b80"
        },
        {
          "url": "https://git.kernel.org/stable/c/49110a8ce654bbe56bef7c5e44cce31f4b102b8a"
        }
      ],
      "title": "ksmbd: validate owner of durable handle on reconnect",
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31717",
    "datePublished": "2026-05-01T13:56:12.012Z",
    "dateReserved": "2026-03-09T15:48:24.134Z",
    "dateUpdated": "2026-08-05T12:24:48.598Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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