CVE-2023-54076 (GCVE-0-2023-54076)

Vulnerability from cvelistv5 – Published: 2025-12-24 12:23 – Updated: 2026-08-05 09:16
VLAI
Title
smb: client: fix missed ses refcounting
Summary
In the Linux kernel, the following vulnerability has been resolved: smb: client: fix missed ses refcounting Use new cifs_smb_ses_inc_refcount() helper to get an active reference of @ses and @ses->dfs_root_ses (if set). This will prevent @ses->dfs_root_ses of being put in the next call to cifs_put_smb_ses() and thus potentially causing an use-after-free bug.
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 7033 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 8e3554150d6c80a84b3cb046615d1a0e943811dc , < eb382196e6f6e05cfafdab797840e5a96c6e7bf0 (git)
Affected: 8e3554150d6c80a84b3cb046615d1a0e943811dc , < bf99f6be2d20146942bce6f9e90a0ceef12cbc1e (git)
Affected: f30d226bcc9f0e2d97b4a6e94c43a28148fbeab6 (git)
Affected: c082c3be0f96e759ff2e361d929832fda0b93851 (git)
Affected: 6.2.15 , < 6.3 (semver)
Affected: 6.3.2 , < 6.4 (semver)
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Linux Linux Affected: 6.4
Unaffected: 0 , < 6.4 (semver)
Unaffected: 6.4.7 , ≤ 6.4.* (semver)
Unaffected: 6.5 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/client/dfs.c",
            "fs/smb/client/smb2transport.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "lessThan": "eb382196e6f6e05cfafdab797840e5a96c6e7bf0",
              "status": "affected",
              "version": "8e3554150d6c80a84b3cb046615d1a0e943811dc",
              "versionType": "git"
            },
            {
              "lessThan": "bf99f6be2d20146942bce6f9e90a0ceef12cbc1e",
              "status": "affected",
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              "versionType": "git"
            },
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              "version": "f30d226bcc9f0e2d97b4a6e94c43a28148fbeab6",
              "versionType": "git"
            },
            {
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            },
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            }
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            "fs/smb/client/dfs.c",
            "fs/smb/client/smb2transport.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.4"
            },
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.4.7",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "6.5",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.4.7",
                  "versionStartIncluding": "6.4",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.5",
                  "versionStartIncluding": "6.4",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
                },
                {
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                  "versionStartIncluding": "6.3.2",
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix missed ses refcounting\n\nUse new cifs_smb_ses_inc_refcount() helper to get an active reference\nof @ses and @ses-\u003edfs_root_ses (if set).  This will prevent\n@ses-\u003edfs_root_ses of being put in the next call to cifs_put_smb_ses()\nand thus potentially causing an use-after-free bug."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The flaw is in the in-kernel SMB/CIFS network filesystem client, and the unbalanced puts are driven by data from the remote peer \u2014 the server picks the SMB2.0/2.1 dialect that routes signing through the buggy `smb2_calc_signature()`, returns the DFS referrals (`DFSREF_REFERRAL_SERVER`) that populate `ses-\u003edfs_root_ses`, and controls the delayed CREATE replies that reach `smb2_handle_cancelled_mid()`. A malicious, compromised, or MITM\u0027d SMB/DFS server drives the refcount underflow purely over the network.\nAC:L - The imbalance is deterministic, not a race: every `smb2_find_smb_ses_unlocked()` acquisition drops one extra reference on `ses-\u003edfs_root_ses` at release, so the attacker simply drives enough signed exchanges to force the count to zero. No memory-layout or timing condition outside the attacker\u0027s control is needed.\nPR:N - The attacker is the remote SMB/DFS server (or a network MITM) and holds no privileges or account on the victim client; referral responses and dialect negotiation happen without any credential on the target system.\nUI:N - The `smb2transport.c` half of the bug is a steady-state runtime path \u2014 on an already-mounted DFS share, signature calculation, cancelled-MID handling, echo keepalives and the DFS cache refresh worker accumulate the extra puts with no user action at attack time.\nS:U - The premature free and subsequent corruption are confined to kernel memory within the same security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Use-after-free on a `cifs_ses` object whose slot can be reoccupied by attacker-groomed heap data yields a read primitive, and the freed session still holds authentication material (`auth_key.response`, signing keys) and kernel pointers used by subsequent code.\nI:H - After the free, `cifs_put_smb_ses()` reads `ses-\u003eserver` from freed memory and performs an indirect call via `server-\u003eops-\u003elogoff()`, giving a control-flow hijack primitive; heap spraying over the freed `cifs_ses` converts this into arbitrary write/code execution.\nA:H - The refcount underflow frees a session still referenced by child sessions, tcons, and the DFS cache worker, reliably producing an oops/panic (and a `WARN_ON(ses-\u003eses_count \u003c 0)`) that takes down the machine."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T09:16:59.986Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/eb382196e6f6e05cfafdab797840e5a96c6e7bf0"
        },
        {
          "url": "https://git.kernel.org/stable/c/bf99f6be2d20146942bce6f9e90a0ceef12cbc1e"
        }
      ],
      "title": "smb: client: fix missed ses refcounting",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2023-54076",
    "datePublished": "2025-12-24T12:23:18.330Z",
    "dateReserved": "2025-12-24T12:21:05.093Z",
    "dateUpdated": "2026-08-05T09:16:59.986Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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      "date": "2026-10-28",
      "epss": "0.00455",
      "percentile": "0.39362"
    },
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                "product": "Linux",
                "programFiles": [
                  "fs/smb/client/dfs.c",
                  "fs/smb/client/smb2transport.c"
                ],
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                    "versionType": "git"
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix missed ses refcounting\n\nUse new cifs_smb_ses_inc_refcount() helper to get an active reference\nof @ses and @ses-\u003edfs_root_ses (if set).  This will prevent\n@ses-\u003edfs_root_ses of being put in the next call to cifs_put_smb_ses()\nand thus potentially causing an use-after-free bug."
          }
        ],
        "id": "CVE-2023-54076",
        "lastModified": "2026-08-04T10:19:27.750",
        "metrics": {
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                "attackVector": "NETWORK",
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                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
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        "vulnStatus": "Deferred"
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      "cve": "CVE-2023-54076",
      "id": "CVE-2023-54076",
      "initial_release_date": "2023-01-01T00:00:00+00:00",
      "product_status:fixed": "279",
      "product_status:known_affected": "22",
      "product_status:known_not_affected": "166",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: smb: client: fix missed ses refcounting",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2023/cve-2023-54076.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-10-17T01:13:33Z",
      "cve": "CVE-2023-54076",
      "id": "CVE-2023-54076",
      "initial_release_date": "2025-12-25T00:56:12Z",
      "product_status:known_affected": "354",
      "product_status:known_not_affected": "283",
      "product_status:recommended": "437",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2023-54076",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2025/cve-2023-54076.json",
      "version": "41"
    }
  }
}



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