CVE-2026-98420 (GCVE-0-2026-98420)
Vulnerability from cvelistv5
Published
2026-10-14 13:27
Modified
2026-10-19 09:19
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: follow SMB2 session expiration semantics ksmbd_session_register() destroys valid sessions after ten seconds of inactivity whenever a client starts another SessionSetup exchange. This confuses Session.IdleTime with Session.ExpirationTime. Windows can create additional authenticated sessions on an existing connection, so deleting the older session invalidates its tree connects and makes mapped drives fail with STATUS_NETWORK_NAME_DELETED. The session expiration rules require the server to change a valid session to expired only after its credential expiration time passes. A valid or expired session otherwise keeps its connection from being scavenged. Connections that have not negotiated a dialect, have no sessions, or have only InProgress sessions are disconnected after an implementation-specific timeout. Use the Windows-compatible 45 second value and run the expiration check periodically for both TCP and SMB Direct. Keep zero as an infinite credential expiration time, and count each Valid-to-Expired transition. Set expired sessions to InProgress when they reauthenticate. If authentication fails, remove the session from the global and per-connection tables immediately, including SMB3 multichannel connections. Retain protection against abandoned SessionId-zero exchanges by allowing only one InProgress authentication per connection. Additional exchanges fail with STATUS_INSUFFICIENT_RESOURCES, and stale InProgress sessions are reaped after the same 45 second setup timeout. This bounds the original unauthenticated memory-exhaustion path without evicting established sessions.
References
Impacted products
Vendor Product Version
Linux Linux Version: ea174a91893956450510945a0c5d1a10b5323656
Version: ea174a91893956450510945a0c5d1a10b5323656
Version: a6a9601ba995d0fec635324cb9fd8d14f9bea14e
Version: 1fc8a2b14ef5223f8e0b95faba2ee0a6e4d0f99d
Version: 750a2d772e9d9ff377fd32e3b6797bf2cd847a7a
Version: 6775ee7ef4b37c521aa4cf3730f54554c4875542
Version: 5.15.145   ≤
Version: 6.1.29   ≤
Version: 6.2.16   ≤
Version: 6.3.2   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/connection.c",
            "fs/smb/server/connection.h",
            "fs/smb/server/mgmt/user_session.c",
            "fs/smb/server/mgmt/user_session.h",
            "fs/smb/server/proc.c",
            "fs/smb/server/server.c",
            "fs/smb/server/smb2pdu.c",
            "fs/smb/server/smb2pdu.h",
            "fs/smb/server/stats.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/connection.c",
            "fs/smb/server/connection.h",
            "fs/smb/server/mgmt/user_session.c",
            "fs/smb/server/mgmt/user_session.h",
            "fs/smb/server/proc.c",
            "fs/smb/server/server.c",
            "fs/smb/server/smb2pdu.c",
            "fs/smb/server/smb2pdu.h",
            "fs/smb/server/stats.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.4"
            },
            {
              "lessThan": "6.4",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.8",
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                  "vulnerable": true
                },
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: follow SMB2 session expiration semantics\n\nksmbd_session_register() destroys valid sessions after ten seconds of\ninactivity whenever a client starts another SessionSetup exchange. This\nconfuses Session.IdleTime with Session.ExpirationTime. Windows can create\nadditional authenticated sessions on an existing connection, so deleting\nthe older session invalidates its tree connects and makes mapped drives\nfail with STATUS_NETWORK_NAME_DELETED.\n\nThe session expiration rules require the server to change a valid session\nto expired only after its credential expiration time passes. A valid or\nexpired session otherwise keeps its connection from being scavenged.\nConnections that have not negotiated a dialect, have no sessions, or have\nonly InProgress sessions are disconnected after an implementation-specific\ntimeout. Use the Windows-compatible 45 second value and run the expiration\ncheck periodically for both TCP and SMB Direct.\n\nKeep zero as an infinite credential expiration time, and count each\nValid-to-Expired transition. Set expired sessions to InProgress when they\nreauthenticate. If authentication fails, remove the session from the\nglobal and per-connection tables immediately, including SMB3 multichannel\nconnections.\n\nRetain protection against abandoned SessionId-zero exchanges by allowing\nonly one InProgress authentication per connection. Additional exchanges\nfail with STATUS_INSUFFICIENT_RESOURCES, and stale InProgress sessions are\nreaped after the same 45 second setup timeout. This bounds the original\nunauthenticated memory-exhaustion path without evicting established\nsessions."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:19:13.954Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/c99ea7855124ca1428a1e59c2b4590aaef34eacf"
        },
        {
          "url": "https://git.kernel.org/stable/c/d7fd1f98607f2cd358e583f9548bdf0173090a86"
        }
      ],
      "title": "ksmbd: follow SMB2 session expiration semantics",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98420",
    "datePublished": "2026-10-14T13:27:49.599Z",
    "dateReserved": "2026-09-25T10:25:14.348Z",
    "dateUpdated": "2026-10-19T09:19:13.954Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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