CVE-2025-21983

Service interruption via non-reclaimable RCU workqueue

Published Apr 1, 2025 · Updated May 11, 2026

Workqueue misconfiguration in the Linux kernel allows local users to interrupt service during RCU memory reclamation. kvfree_rcu() places reclamation work on system_unbound_wq without WQ_MEM_RECLAIM, violating flush-dependency rules when reclaim work waits on it. A low-privileged local user must reach an affected kernel path; the demonstrated NVMe namespace-removal path produces a kernel warning and can block reclamation progress.

CVSS severity7.8
High
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Workqueue misconfiguration in the Linux kernel allows local users to interrupt service during RCU memory reclamation. kvfree_rcu() places reclamation work on system_unbound_wq without WQ_MEM_RECLAIM, violating flush-dependency rules when reclaim work waits on it. A low-privileged local user must reach an affected kernel path; the demonstrated NVMe namespace-removal path produces a kernel warning and can block reclamation progress.

The record

CVE
CVE-2025-21983
Published
Apr 1, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=6.12
  2. Affected versionversion=6c6c47b063b593785202be158e61fe5c827d6677 <656e35bf66a11e1adde44c4c12050086dc39f241
  3. Affected versionversion=6c6c47b063b593785202be158e61fe5c827d6677 <a74979dce9e9c61f6d797c3761020252c4d8dc63
  4. Affected versionversion=6c6c47b063b593785202be158e61fe5c827d6677 <dfd3df31c9db752234d7d2e09bef2aeabb643ce4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.12; version=6c6c47b063b593785202be158e61fe5c827d6677 <656e35bf66a11e1adde44c4c12050086dc39f241; version=6c6c47b063b593785202be158e61fe5c827d6677 <a74979dce9e9c61f6d797c3761020252c4d8dc63; version=6c6c47b063b593785202be158e61fe5c827d6677 <dfd3df31c9db752234d7d2e09bef2aeabb643ce4

Published CVSS scores

7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
5.5SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.8SUSECVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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