CVE-2026-53321

Task stall via uncapped NAPI busy-poll timeout

Published Jun 26, 2026 · Updated Jun 26, 2026

Denial of service in Linux Kernel 6.9 and later allows local users to stall a task through an excessive io_uring NAPI busy-poll timeout. io_register_napi accepts the user-supplied busy_poll_to value without a cap, while the no-event polling loop performs no conditional rescheduling. A local user must create an io_uring instance and enable NAPI busy polling; an extreme timeout can trigger stuck-task complaints and interrupt service.

CVSS severity5.5
Medium
EPSS probability0.11%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Linux Kernel 6.9 and later allows local users to stall a task through an excessive io_uring NAPI busy-poll timeout. io_register_napi accepts the user-supplied busy_poll_to value without a cap, while the no-event polling loop performs no conditional rescheduling. A local user must create an io_uring instance and enable NAPI busy polling; an extreme timeout can trigger stuck-task complaints and interrupt service.

The record

CVE
CVE-2026-53321
Published
Jun 26, 2026
Updated
Jun 26, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.9
  2. Affected versionversion=8d0c12a80cdeb80d5e0510e96d38fe551ed8e9b5 <39767f944a8c9e696566c37ad5b20131406c4b8d
  3. Affected versionversion=8d0c12a80cdeb80d5e0510e96d38fe551ed8e9b5 <cb3af525f8dfb8930f0c123e5755fa967a12d5c1
  4. Affected versionversion=8d0c12a80cdeb80d5e0510e96d38fe551ed8e9b5 <df8599ee18c0e5fe343ffe0b4c379636b8bb839a

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=6.9; version=8d0c12a80cdeb80d5e0510e96d38fe551ed8e9b5 <39767f944a8c9e696566c37ad5b20131406c4b8d; version=8d0c12a80cdeb80d5e0510e96d38fe551ed8e9b5 <cb3af525f8dfb8930f0c123e5755fa967a12d5c1; version=8d0c12a80cdeb80d5e0510e96d38fe551ed8e9b5 <df8599ee18c0e5fe343ffe0b4c379636b8bb839a

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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