FKIE_CVE-2026-31718

Vulnerability from fkie_nvd - Published: 2026-05-01 14:16 - Updated: 2026-05-17 16:16
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 __ksmbd_close_fd() via durable scavenger When a durable file handle survives session disconnect (TCP close without SMB2_LOGOFF), session_fd_check() sets fp->conn = NULL to preserve the handle for later reconnection. However, it did not clean up the byte-range locks on fp->lock_list. Later, when the durable scavenger thread times out and calls __ksmbd_close_fd(NULL, fp), the lock cleanup loop did: spin_lock(&fp->conn->llist_lock); This caused a slab use-after-free because fp->conn was NULL and the original connection object had already been freed by ksmbd_tcp_disconnect(). The root cause is asymmetric cleanup: lock entries (smb_lock->clist) were left dangling on the freed conn->lock_list while fp->conn was nulled out. To fix this issue properly, we need to handle the lifetime of smb_lock->clist across three paths: - Safely skip clist deletion when list is empty and fp->conn is NULL. - Remove the lock from the old connection's lock_list in session_fd_check() - Re-add the lock to the new connection's lock_list in ksmbd_reopen_durable_fd().
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0000a7780e0e446a28a273572f6ea8f7f582f694
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/235e32320a470fcd3998fb3774f2290a0eb302a1Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3d6682726c2d3a46d31dae88b8166786b09b03adPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b34fc42cfe922e551f7a27d3ac3bb016e41d7dd9Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e33c65f011980b4ad4abfd93585ec2079856368fPatch
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel 7.1
To clipboard 

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger\n\nWhen a durable file handle survives session disconnect (TCP close without\nSMB2_LOGOFF), session_fd_check() sets fp-\u003econn = NULL to preserve the\nhandle for later reconnection. However, it did not clean up the byte-range\nlocks on fp-\u003elock_list.\n\nLater, when the durable scavenger thread times out and calls\n__ksmbd_close_fd(NULL, fp), the lock cleanup loop did:\n\n    spin_lock(\u0026fp-\u003econn-\u003ellist_lock);\n\nThis caused a slab use-after-free because fp-\u003econn was NULL and the\noriginal connection object had already been freed by\nksmbd_tcp_disconnect().\n\nThe root cause is asymmetric cleanup: lock entries (smb_lock-\u003eclist) were\nleft dangling on the freed conn-\u003elock_list while fp-\u003econn was nulled out.\n\nTo fix this issue properly, we need to handle the lifetime of\nsmb_lock-\u003eclist across three paths:\n - Safely skip clist deletion when list is empty and fp-\u003econn is NULL.\n - Remove the lock from the old connection\u0027s lock_list in\n   session_fd_check()\n - Re-add the lock to the new connection\u0027s lock_list in\n   ksmbd_reopen_durable_fd()."
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  "id": "CVE-2026-31718",
  "lastModified": "2026-05-17T16:16:16.300",
  "metrics": {
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          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
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}


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