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🛡️ CVE-2023-53531 — kernel

🟠 CVSS 7.8 — High ✅ No Known Exploit NVD
7.8
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

null_blk: fix poll request timeout handling

In the Linux kernel, the following vulnerability has been resolved:

null_blk: fix poll request timeout handling

When doing io_uring benchmark on /dev/nullb0, it's easy to crash the

kernel if poll requests timeout triggered, as reported by David. [1]

BUG: kernel NULL pointer dereference, address: 0000000000000008

Workqueue: kblockd blk_mq_timeout_work

RIP: 0010:null_timeout_rq+0x4e/0x91

Call Trace:

? null_timeout_rq+0x4e/0x91

blk_mq_handle_expired+0x31/0x4b

bt_iter+0x68/0x84

? bt_tags_iter+0x81/0x81

__sbitmap_for_each_set.constprop.0+0xb0/0xf2

? __blk_mq_complete_request_remote+0xf/0xf

bt_for_each+0x46/0x64

? __blk_mq_complete_request_remote+0xf/0xf

? percpu_ref_get_many+0xc/0x2a

blk_mq_queue_tag_busy_iter+0x14d/0x18e

blk_mq_timeout_work+0x95/0x127

process_one_work+0x185/0x263

worker_thread+0x1b5/0x227

This is indeed a race problem between null_timeout_rq() and null_poll().

null_poll() null_timeout_rq()

spin_lock(&nq->poll_lock)

list_splice_init(&nq->poll_list, &list)

spin_unlock(&nq->poll_lock)

while (!list_empty(&list))

req = list_first_entry()

list_del_init()

...

blk_mq_add_to_batch()

// req->rq_next = NULL

spin_lock(&nq->poll_lock)

// rq->queuelist->next == NULL

list_del_init(&rq->queuelist)

spin_unlock(&nq->poll_lock)

Fix these problems by setting requests state to MQ_RQ_COMPLETE under

nq->poll_lock protection, in which null_timeout_rq() can safely detect

this race and early return.

Note this patch just fix the kernel panic when request timeout happen.

[1] https://lore.kernel.org/all/[email protected]/

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

  • Attack vector: Local — a local account, shell or session on the host is needed.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: Low — an ordinary user account is enough.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: High — total loss, or loss the attacker controls.

Affected software

CVE-2023-53531 is recorded against 2 packages.

  • kernel (from 6.2.0 up to 6.5.4)
  • linux-kernel (from 6.2 up to 6.5.4)

Timeline and source

Published on 1 October 2025 and last revised on 12 August 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
github.com (Advisory)
nvd.nist.gov (Advisory)
git.kernel.org (Package)

Other advisories for this package

kernel has other advisories on record. If you are patching this one, these are worth checking on the same host:

CVE-2023-53531 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity High
CVSS Score 7.8
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2025-10-01
Updated 2026-08-20
Modified 2026-08-12

Affected Packages

Software From version Fixed in
kernel 6.2.0 6.5.4
linux-kernel 6.2 6.5.4

Similar Threats

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