CVE-2026-64140 (GCVE-0-2026-64140)
Vulnerability from cvelistv5
Published
2026-07-19 15:40
Modified
2026-08-05 12:39
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix null pointer dereference in proc_show_files() When a SMB2 client opens a file with a durable v2 handle and then issues SMB2 SESSION_LOGOFF, session_fd_check() clears fp->tcon = NULL on the reconnectable file pointer but leaves the fp registered in global_ft.idr until the durable scavenger fires (up to fp->durable_timeout seconds later). During that window any read of /proc/fs/ksmbd/files (mode 0400) panics the kernel because proc_show_files() walks global_ft.idr and unconditionally dereferences fp->tcon->id with no NULL guard. Reproducer requires only a successful SMB2 SESSION_SETUP and a share configured with 'durable handles = yes'. KASAN report on mainline 70390501d194: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:proc_show_files+0x118/0x740 Call Trace: proc_show_files+0x118/0x740 seq_read_iter+0x4ef/0xe10 proc_reg_read_iter+0x1b7/0x280 ... Guard the dereference. A durable-disconnected fp legitimately has no tcon; report its tree id as 0 rather than oopsing.
References
Impacted products
Vendor Product Version
Linux Linux Version: b38f99c1217ae04753340f0fdcd8f35bf56841dc
Version: b38f99c1217ae04753340f0fdcd8f35bf56841dc
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/vfs_cache.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "8eab081627b67216d1c8f638b68289b500dc9a6b",
              "status": "affected",
              "version": "b38f99c1217ae04753340f0fdcd8f35bf56841dc",
              "versionType": "git"
            },
            {
              "lessThan": "904901561e61a2b559070b20c74a8c95491f30aa",
              "status": "affected",
              "version": "b38f99c1217ae04753340f0fdcd8f35bf56841dc",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/vfs_cache.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.0"
            },
            {
              "lessThan": "7.0",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.11",
              "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": "7.0.11",
                  "versionStartIncluding": "7.0",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "7.0",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix null pointer dereference in proc_show_files()\n\nWhen a SMB2 client opens a file with a durable v2 handle and then issues\nSMB2 SESSION_LOGOFF, session_fd_check() clears fp-\u003etcon = NULL on the\nreconnectable file pointer but leaves the fp registered in global_ft.idr\nuntil the durable scavenger fires (up to fp-\u003edurable_timeout seconds\nlater).\n\nDuring that window any read of /proc/fs/ksmbd/files (mode 0400) panics\nthe kernel because proc_show_files() walks global_ft.idr and\nunconditionally dereferences fp-\u003etcon-\u003eid with no NULL guard.\n\nReproducer requires only a successful SMB2 SESSION_SETUP and a share\nconfigured with \u0027durable handles = yes\u0027. KASAN report on mainline\n70390501d194:\n\n  general protection fault, probably for non-canonical address\n  0xdffffc0000000000: 0000 [#1] SMP KASAN PTI\n  KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]\n  RIP: 0010:proc_show_files+0x118/0x740\n  Call Trace:\n   proc_show_files+0x118/0x740\n   seq_read_iter+0x4ef/0xe10\n   proc_reg_read_iter+0x1b7/0x280\n   ...\n\nGuard the dereference. A durable-disconnected fp legitimately has no\ntcon; report its tree id as 0 rather than oopsing."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The poisoned durable-handle state is created remotely over ksmbd\u0027s TCP/445 SMB2 path (SESSION_SETUP, TREE_CONNECT, CREATE with durable v2, SESSION_LOGOFF); ksmbd is a network-facing in-kernel SMB server per kernel CVSS guidance.\nAC:L - An attacker fully controls the SMB2 sequence that leaves `fp-\u003etcon = NULL` while the file remains in `global_ft.idr`; once that state exists, any read of `/proc/fs/ksmbd/files` deterministically oopses, and the window lasts up to `fp-\u003edurable_timeout` seconds (repeatable).\nPR:N - Exploitation requires only network reachability to ksmbd plus a successful SMB2 SESSION_SETUP (guest or any configured share account); no host root or kernel capabilities are needed on the attacker side to plant the corrupt durable-handle entry.\nUI:N - No victim user action (opening files, mounting shares, clicking links) is required; the crash is triggered by kernel procfs iteration, not by end-user interaction.\nS:U - Impact is a kernel NULL pointer dereference/panic within the ksmbd/kernel security authority; it does not cross VM, IOMMU, or sandbox boundaries.\nC:N - This is a pure NULL pointer dereference at `fp-\u003etcon-\u003eid` with no out-of-bounds read, UAF, or other memory corruption that could leak kernel data.\nI:N - The bug is a read of address 0 through a NULL `fp-\u003etcon` pointer; it provides no write primitive, type confusion, or control-flow hijack opportunity.\nA:H - Unconditional dereference of NULL `fp-\u003etcon` in `proc_show_files()` causes a kernel general protection fault/oops (KASAN null-ptr-deref), crashing or severely disrupting the host."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:39:40.506Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/8eab081627b67216d1c8f638b68289b500dc9a6b"
        },
        {
          "url": "https://git.kernel.org/stable/c/904901561e61a2b559070b20c74a8c95491f30aa"
        }
      ],
      "title": "ksmbd: fix null pointer dereference in proc_show_files()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64140",
    "datePublished": "2026-07-19T15:40:33.194Z",
    "dateReserved": "2026-07-19T07:54:57.037Z",
    "dateUpdated": "2026-08-05T12:39:40.506Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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