CVE-2025-21807

Local block-device hang via inverted queue locking

Published Feb 27, 2025 · Updated Jul 18, 2026

Improper locking in the Linux kernel block sysfs code allows local users to hang block-device operations via concurrent limit updates. queue_attr_store() freezes the device queue before store_limit() takes the limits lock, while driver revalidation can hold that lock and issue commands requiring the queue. Reachability requires permission to modify a queue limit while a driver such as SCSI sd revalidates hardware limits; the bounded consequence is an availability hang.

CVSS severity5.5
Medium
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper locking in the Linux kernel block sysfs code allows local users to hang block-device operations via concurrent limit updates. queue_attr_store() freezes the device queue before store_limit() takes the limits lock, while driver revalidation can hold that lock and issue commands requiring the queue. Reachability requires permission to modify a queue limit while a driver such as SCSI sd revalidates hardware limits; the bounded consequence is an availability hang.

The record

CVE
CVE-2025-21807
Published
Feb 27, 2025
Updated
Jul 18, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 27, 2025CVE publishedPublication date reported by the CVE source.
  2. Jul 18, 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=0327ca9d53bfbb0918867313049bba7046900f73 <1645cd7fd42c236c952e9228badcac4fea1829ea
  2. Affected versionversion=0327ca9d53bfbb0918867313049bba7046900f73 <8985da5481562e96b95e94ed8e5cc9b6565eb82b
  3. Affected versionversion=0327ca9d53bfbb0918867313049bba7046900f73 <c99f66e4084a62a2cc401c4704a84328aeddc9ec
  4. Affected versionversion=6.9

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=0327ca9d53bfbb0918867313049bba7046900f73 <1645cd7fd42c236c952e9228badcac4fea1829ea; version=0327ca9d53bfbb0918867313049bba7046900f73 <8985da5481562e96b95e94ed8e5cc9b6565eb82b; version=0327ca9d53bfbb0918867313049bba7046900f73 <c99f66e4084a62a2cc401c4704a84328aeddc9ec; version=6.9

Published CVSS scores

5.5Amazon LinuxCVSS: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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