CVE-2026-31718

Critical

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().

Package Linux Kernel
Published 2026-05-01
Last modified 2026-05-17
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

9.8

out of 10
Critical
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Weakness type

CWE-416

CVE-2026-31718 is a Use After Free vulnerability

What is Use After Free?

The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. Learn more on MITRE CWE

Affected versions

Linux kernel versions 6.6.32, 6.9 and later are affected. Fixed in 6.6.140, 6.12.84, 6.18.25, 7.0.2, 7.1-rc1 and their respective stable series.

Affected from
≥ 6.6.32 ≥ 6.9
Fixed in
✓ 6.6.140 6.6.x ✓ 6.12.84 6.12.x ✓ 6.18.25 6.18.x ✓ 7.0.2 7.0.x ✓ 7.1-rc1

References

The following references provide additional information about CVE-2026-31718 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

5 patch commits total View all on NVD

Frequently asked questions

  • What is CVE-2026-31718?

    CVE-2026-31718 is a Critical severity Linux kernel vulnerability with a CVSS score of 9.8 out of 10 , classified as an Use After Free flaw (CWE-416) . It affects Linux kernel versions from 6.6.32 onward and has been patched in 6.6.140, 6.12.84, 6.18.25 and others. CVE-2026-31718 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2026-31718?

    CVE-2026-31718 has a CVSS score of 9.8 out of 10, rated Critical severity (CVSS 3.1). The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H .

  • Is there a patch available for CVE-2026-31718?

    Yes — CVE-2026-31718 has been patched. Fixed versions include 6.6.140, 6.12.84, 6.18.25 and others. If you are running Linux kernel 6.6.32 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2026-31718 actively exploited?

    No — CVE-2026-31718 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

  • What is Use After Free (CWE-416)?

    The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. View CWE-416 on MITRE CWE →

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