CVE-2026-43379 (GCVE-0-2026-43379)
Vulnerability from cvelistv5
Published
2026-05-08 14:21
Modified
2026-08-05 12:27
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in smb_lazy_parent_lease_break_close() opinfo pointer obtained via rcu_dereference(fp->f_opinfo) is being accessed after rcu_read_unlock() has been called. This creates a race condition where the memory could be freed by a concurrent writer between the unlock and the subsequent pointer dereferences (opinfo->is_lease, etc.), leading to a use-after-free.
References
Impacted products
Vendor Product Version
Linux Linux Version: 27b40b7bfcd121fe13a150ffe11957630cf49246
Version: 5fb282ba4fef8985a5acf2b32681f2ec07732561
Version: 5fb282ba4fef8985a5acf2b32681f2ec07732561
Version: 5fb282ba4fef8985a5acf2b32681f2ec07732561
Version: 5fb282ba4fef8985a5acf2b32681f2ec07732561
Version: 6.6.32   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/oplock.c"
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        },
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          "product": "Linux",
          "programFiles": [
            "fs/smb/server/oplock.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.9"
            },
            {
              "lessThan": "6.9",
              "status": "unaffected",
              "version": "0",
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              "status": "unaffected",
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              "status": "unaffected",
              "version": "6.12.78",
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              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.19",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.130",
                  "versionStartIncluding": "6.6.32",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.78",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                },
                {
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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: fix use-after-free in smb_lazy_parent_lease_break_close()\n\nopinfo pointer obtained via rcu_dereference(fp-\u003ef_opinfo) is being\naccessed after rcu_read_unlock() has been called. This creates a\nrace condition where the memory could be freed by a concurrent\nwriter between the unlock and the subsequent pointer dereferences\n(opinfo-\u003eis_lease, etc.), leading to a use-after-free."
        }
      ],
      "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 - ksmbd processes SMB2 traffic over the network on TCP/445, and the vulnerable close path is reached through SMB2 create/write/close requests from a remote client.\nAC:L - The attacker can create v2 lease state, trigger `reserve_lease_break` with SMB2 write, and repeatedly drive concurrent close/opinfo teardown using their own SMB requests or connections. The race is attacker-influenced and repeatable, so no external uncontrollable condition is required.\nPR:N - The path is post-session/tree-connect, but ksmbd supports guest/anonymous sessions and guest-access shares; in that reasonable deployment no prior credentials are needed. Under the required higher-severity rule, this is scored as no privileges required.\nUI:N - No victim user action is required after the ksmbd service and share are available; the attacker sends SMB requests directly.\nS:U - The vulnerable component and impacted resources are the same kernel/ksmbd security authority. This is not a VM escape, IOMMU bypass, or cross-scope boundary violation.\nC:H - This is a use-after-free of `oplock_info`/lease state after dropping the RCU read lock. Freed kernel objects may be reclaimed and shaped through repeated SMB activity, making high confidentiality impact defensible.\nI:H - Use-after-free in kernel heap objects can be leveraged beyond a crash through object reuse and control-flow or data-structure corruption. Following the required UAF guidance, integrity impact is high.\nA:H - Even without full exploitation, dereferencing freed `oplock_info` or `o_lease` memory can cause a kernel oops or panic. The vulnerable path is remotely triggerable and repeatable, so availability impact is high."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:27:39.686Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/bf4d66d72e4a9e268c1012c331ce9eaedb5e2086"
        },
        {
          "url": "https://git.kernel.org/stable/c/960699317d39f46611f4ebeb69edc567c1f4e6b6"
        },
        {
          "url": "https://git.kernel.org/stable/c/dbbd328cf58261ca239756fe1c0d10c9518d3399"
        },
        {
          "url": "https://git.kernel.org/stable/c/b3568347c51c46e2cabc356bc34676df98296619"
        },
        {
          "url": "https://git.kernel.org/stable/c/eac3361e3d5dd8067b3258c69615888eb45e9f25"
        }
      ],
      "title": "ksmbd: fix use-after-free in smb_lazy_parent_lease_break_close()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43379",
    "datePublished": "2026-05-08T14:21:28.027Z",
    "dateReserved": "2026-05-01T14:12:56.006Z",
    "dateUpdated": "2026-08-05T12:27:39.686Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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