CVE-2025-21909

Kernel warning via conflicting monitor-mode flags

Published Apr 1, 2025 · Updated May 11, 2026

Improper nl80211 flag validation in Linux allows local users to trigger a kernel warning by creating and deleting a monitor interface. Cooked mode takes precedence over active mode, leaving the sub-interface without IEEE80211_SDATA_IN_DRIVER before check_sdata_in_driver() examines it during deletion. The path requires low-privileged local access and a wireless monitor interface; the published record establishes WARN_ONCE(), not a crash or hang.

CVSS severity5.5
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper nl80211 flag validation in Linux allows local users to trigger a kernel warning by creating and deleting a monitor interface. Cooked mode takes precedence over active mode, leaving the sub-interface without IEEE80211_SDATA_IN_DRIVER before check_sdata_in_driver() examines it during deletion. The path requires low-privileged local access and a wireless monitor interface; the published record establishes WARN_ONCE(), not a crash or hang.

The record

CVE
CVE-2025-21909
Published
Apr 1, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-362
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=2.6.26
  2. Affected versionversion=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <236f41ca728f23210b31ed2d1d8a6df575a4b2d6
  3. Affected versionversion=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <351eb7ac53ff1cd94d893c0c4534ced2f36ae7d7
  4. Affected versionversion=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <49f27f29446a5bfe633dd2cc0cfebd48a1a5e77f
  5. Affected versionversion=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <521e55c2b0d6028861ac0a2d06aa57bb0e3ac486
  6. Affected versionversion=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <5ea856d93794c4afa5542defd8c61f2708dc245a
  7. Affected versionversion=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <ac4860141300581d3e2f6c6dafa37220f7ea9f65
  8. Affected versionversion=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <cd1bdcb77fdc03c253137e55bae10551b3481461
  9. Affected versionversion=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <ebebbb0eded2ed9a1abfa31962f6fb699e6abce7

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.26; version=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <236f41ca728f23210b31ed2d1d8a6df575a4b2d6; version=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <351eb7ac53ff1cd94d893c0c4534ced2f36ae7d7; version=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <49f27f29446a5bfe633dd2cc0cfebd48a1a5e77f; version=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <521e55c2b0d6028861ac0a2d06aa57bb0e3ac486; version=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <5ea856d93794c4afa5542defd8c61f2708dc245a; version=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <ac4860141300581d3e2f6c6dafa37220f7ea9f65; version=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <cd1bdcb77fdc03c253137e55bae10551b3481461; version=66f7ac50ed7cc5c19a62bc97e8f6e7891004a03a <ebebbb0eded2ed9a1abfa31962f6fb699e6abce7

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

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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