CVE-2026-52911 (GCVE-0-2026-52911)
Vulnerability from cvelistv5
Published
2026-06-21 06:18
Modified
2026-08-05 12:31
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: scope conn->binding slowpath to bound sessions only When the binding SESSION_SETUP sets conn->binding = true, the flag stays set after the call so that the global session lookup in ksmbd_session_lookup_all() can find the session, which was not added to conn->sessions. Because the flag is connection-wide, the global lookup path will also resolve any other session by id if asked. Tighten the global lookup so that the returned session must have this connection registered in its channel xarray (sess->ksmbd_chann_list). The channel entry is installed by the existing binding_session path in ntlm_authenticate()/krb5_authenticate() when a SESSION_SETUP completes successfully, so this condition is a strict equivalent of "this connection has been accepted as a channel of this session". Connections that have not bound to a given session cannot reach it via the global table. The existing conn->binding gate for entering the slowpath is preserved so that non-binding connections keep the fast-path-only behavior, and the session->state check is unchanged.
References
Impacted products
Vendor Product Version
Linux Linux Version: f5a544e3bab78142207e0242d22442db85ba1eff
Version: f5a544e3bab78142207e0242d22442db85ba1eff
Version: f5a544e3bab78142207e0242d22442db85ba1eff
Version: f5a544e3bab78142207e0242d22442db85ba1eff
Version: f5a544e3bab78142207e0242d22442db85ba1eff
Version: f5a544e3bab78142207e0242d22442db85ba1eff
Version: f5a544e3bab78142207e0242d22442db85ba1eff
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/mgmt/user_session.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "5.15"
            },
            {
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              "version": "0",
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              "version": "5.15.209",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.175",
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            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.141",
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            },
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              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.91",
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            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.33",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.10",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.209",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.175",
                  "versionStartIncluding": "5.15",
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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: scope conn-\u003ebinding slowpath to bound sessions only\n\nWhen the binding SESSION_SETUP sets conn-\u003ebinding = true, the flag stays\nset after the call so that the global session lookup in\nksmbd_session_lookup_all() can find the session, which was not added to\nconn-\u003esessions. Because the flag is connection-wide, the global lookup\npath will also resolve any other session by id if asked.\n\nTighten the global lookup so that the returned session must have this\nconnection registered in its channel xarray (sess-\u003eksmbd_chann_list).\nThe channel entry is installed by the existing binding_session path in\nntlm_authenticate()/krb5_authenticate() when a SESSION_SETUP completes\nsuccessfully, so this condition is a strict equivalent of \"this\nconnection has been accepted as a channel of this session\". Connections\nthat have not bound to a given session cannot reach it via the global\ntable.\n\nThe existing conn-\u003ebinding gate for entering the slowpath is preserved\nso that non-binding connections keep the fast-path-only behavior, and\nthe session-\u003estate check is unchanged."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.8,
            "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"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - ksmbd is an in-kernel SMB server reachable over the network via SMB over TCP/RDMA, and the vulnerable session lookup is reached while processing remote SMB2/SMB3 requests.\nAC:L - After a successful SMB3 multichannel binding, the connection-wide binding flag remains set and the attacker can send ordinary subsequent SMB requests with chosen SessionIds. Session and tree IDs are low allocated identifiers, and no condition outside attacker control is required for the vulnerable lookup once binding state is established.\nPR:L - The durable exploit path requires the attacker to authenticate and successfully perform a non-guest multichannel binding SESSION_SETUP, which requires a valid low-privileged SMB account/session. The fixed issue is post-success binding state rather than a purely pre-authentication path.\nUI:N - No victim user action is required; the attacker sends SMB protocol messages directly to the ksmbd service.\nS:U - The impact remains within the kernel/ksmbd server security authority and exposed SMB resources. It does not cross a hypervisor, sandbox, or other separate security authority boundary.\nC:H - The bug allows a bound connection to resolve unrelated valid sessions by ID from the global session table, enabling access as another SMB session/user. In a reasonable deployment this can expose all files and share data accessible to the victim session.\nI:H - By obtaining another user\u0027s session context, the attacker can perform SMB operations as that user, including writes, deletes, metadata changes, or administrative IPC allowed to the victim. This is a high integrity impact on SMB-served data.\nA:H - The attacker can issue operations such as LOGOFF or destructive file/share operations against other resolved sessions, disrupting victim access and SMB-served data availability. This can be repeated remotely against the service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:31:34.753Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/e74c00c6af428a39e564cdc5bd3a3648c6d8de87"
        },
        {
          "url": "https://git.kernel.org/stable/c/e3a93ce6e25757b8f375e38b8f91e1d9da4edc1a"
        },
        {
          "url": "https://git.kernel.org/stable/c/1ff46c9915c1cbf454db58a8cb87f7cac818e6a6"
        },
        {
          "url": "https://git.kernel.org/stable/c/974c1c224e85549dc3459f3bb2255bbbdd2b9372"
        },
        {
          "url": "https://git.kernel.org/stable/c/2cc8a4db633b10715450b291c1343859a4b2c509"
        },
        {
          "url": "https://git.kernel.org/stable/c/1e2bec062c5c9ec282636715166056d0998d746d"
        },
        {
          "url": "https://git.kernel.org/stable/c/b0da97c034b6107d14e537e212d4ce8b22109a58"
        }
      ],
      "title": "ksmbd: scope conn-\u003ebinding slowpath to bound sessions only",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-52911",
    "datePublished": "2026-06-21T06:18:49.342Z",
    "dateReserved": "2026-06-09T07:44:35.366Z",
    "dateUpdated": "2026-08-05T12:31:34.753Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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