CVE-2026-80926 (GCVE-0-2026-80926)
Vulnerability from cvelistv5
Published
2026-09-11 19:37
Modified
2026-10-19 08:45
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 oplock break notification smb2_oplock_break_noti() reads opinfo->conn without any lock and dereferences it after two allocations which may sleep. When the durable handle owning the oplock is disconnected, session_fd_check() clears opinfo->conn and drops its conn reference under ci->m_lock, and the last ksmbd_conn_put() frees the connection. A break triggered by another connection that races with the teardown can then resurrect the freed connection: ksmbd_conn_get() is a plain atomic_inc, and the queued break work later dereferences the stale conn via ksmbd_conn_write(), a use-after-free reachable by any authenticated client holding a durable batch oplock. Thread the caller's inode into the notification path instead of taking a new reference on it. Every caller of oplock_break() already holds a live ksmbd_file (or an explicit ksmbd_inode_lookup_lock() reference, in the parent lease break paths) on the inode that owns the break target's oplock list, so ci cannot be freed during the call, and its lock can be taken without dereferencing opinfo->o_fp, which a concurrent close may free. Select and pin the connection under ci->m_lock, the same lock session_fd_check() and ksmbd_reopen_durable_fd() use to update opinfo->conn, so a concurrent detach either loses the race to the clear or keeps the connection alive until the notification work releases it. Transfer the reference to the work item and release it on allocation failures.
References
Impacted products
Vendor Product Version
Linux Linux Version: 945a86b21b40fb17183f5b27461baa6f03e2467f
Version: 1ff58dcfcab434ebb51649da33774fbb8e1f7b67
Version: e735dbd489e3ea02be78dba991056fe1138be51e
Version: b003086d76968298f22e7cf62239833b5a3a06b1
Version: b003086d76968298f22e7cf62239833b5a3a06b1
Version: 75e33deda658c1ab3a9336cbdb1436536f9b3660
Version: 6.6.143   ≤
Version: 6.12.94   ≤
Version: 6.18.36   ≤
Version: 7.0.13   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/oplock.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
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              "status": "affected",
              "version": "7.0.13",
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            }
          ]
        },
        {
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          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.1"
            },
            {
              "lessThan": "7.1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.158",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.111",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.51",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.5",
              "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": "6.6.158",
                  "versionStartIncluding": "6.6.143",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.111",
                  "versionStartIncluding": "6.12.94",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.5",
                  "versionStartIncluding": "7.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "7.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "7.0.13",
                  "vulnerable": true
                }
              ],
              "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 oplock break notification\n\nsmb2_oplock_break_noti() reads opinfo-\u003econn without any lock and\ndereferences it after two allocations which may sleep.  When the\ndurable handle owning the oplock is disconnected, session_fd_check()\nclears opinfo-\u003econn and drops its conn reference under ci-\u003em_lock, and\nthe last ksmbd_conn_put() frees the connection.  A break triggered by\nanother connection that races with the teardown can then resurrect the\nfreed connection: ksmbd_conn_get() is a plain atomic_inc, and the\nqueued break work later dereferences the stale conn via\nksmbd_conn_write(), a use-after-free reachable by any authenticated\nclient holding a durable batch oplock.\n\nThread the caller\u0027s inode into the notification path instead of taking\na new reference on it.  Every caller of oplock_break() already holds a\nlive ksmbd_file (or an explicit ksmbd_inode_lookup_lock() reference,\nin the parent lease break paths) on the inode that owns the break\ntarget\u0027s oplock list, so ci cannot be freed during the call, and its\nlock can be taken without dereferencing opinfo-\u003eo_fp, which a\nconcurrent close may free.  Select and pin the connection under\nci-\u003em_lock, the same lock session_fd_check() and\nksmbd_reopen_durable_fd() use to update opinfo-\u003econn, so a concurrent\ndetach either loses the race to the clear or keeps the connection\nalive until the notification work releases it.  Transfer the reference\nto the work item and release it on allocation failures."
        }
      ],
      "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 is the in-kernel SMB server on TCP/445; smb2_oplock_break_noti() is reached from remote SMB2 CREATE/WRITE/truncate that breaks a durable batch oplock, and the racing teardown is a remote disconnect or SMB2 LOGOFF, so a network peer fully drives the UAF.\nAC:L - The attacker controls both sides of the race: one connection holds a durable batch oplock while a second opens the same file to force oplock_break(), and dropping the first connection runs session_fd_check() during the sleeping allocations before ksmbd_conn_get(); the window is retryable.\nPR:N - ksmbd shares are commonly exposed with guest/anonymous mapping, so a remote client can SESSION_SETUP, TREE_CONNECT, CREATE a durable batch oplock, and trigger the racing disconnect without a privileged host account; no meaningful credential gate protects this path.\nUI:N - No victim action is required; the attacker opens both SMB connections, requests the durable batch oplock, forces the conflicting open, and drops the first connection entirely on their own.\nS:U - The freed ksmbd_conn and resulting kernel heap corruption stay within the ksmbd/kernel security authority on the SMB server host; this is not a VM, IOMMU, or sandbox escape.\nC:H - Use-after-free of struct ksmbd_conn lets the attacker reclaim the slab object; __smb2_oplock_break_noti() then reads conn-\u003etransport and related fields from attacker-controlled memory, enabling kernel pointer and data disclosure.\nI:H - ksmbd_conn_write() calls conn-\u003etransport-\u003eops-\u003ewritev and ksmbd_conn_lock() on the freed object, so heap spraying the reclaimed ksmbd_conn yields an arbitrary function-pointer call and mutex writes into attacker-chosen memory.\nA:H - Even without a fully controlled exploit, using a freed ksmbd_conn (mutex lock, transport dereference, r_count/waitqueue) causes kernel memory corruption, oops, or panic and takes down the host."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:45:10.176Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/892f643b141aee3f7aa7c0fc61ddcb55c59f1996"
        },
        {
          "url": "https://git.kernel.org/stable/c/5de0527f782430b1109a447646e32033ad018a6a"
        },
        {
          "url": "https://git.kernel.org/stable/c/c8279ae8df68cce9cd3b785e85f7a86c80a46e78"
        },
        {
          "url": "https://git.kernel.org/stable/c/8cc98db4fc590e6c7d9db6529320982ee16c5d1d"
        },
        {
          "url": "https://git.kernel.org/stable/c/0e753899627b5e28a9fea8bca98262a6f65a2452"
        }
      ],
      "title": "ksmbd: fix use-after-free in oplock break notification",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80926",
    "datePublished": "2026-09-11T19:37:29.855Z",
    "dateReserved": "2026-08-26T14:34:25.802Z",
    "dateUpdated": "2026-10-19T08:45:10.176Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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