CVE-2021-47091Public exploit

Kernel availability loss via unlocked channel-context release

Published Mar 4, 2024 · Updated May 11, 2026

Improper locking in mac80211 in Linux allows local users to cause kernel availability loss by triggering a failed access-point start. On the ieee80211_start_ap error path in net/mac80211/cfg.c, the kernel calls ieee80211_vif_release_channel without holding local->mtx, despite its lock assertion. The public reproducer reaches a kernel warning rather than demonstrating data disclosure or code execution.

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 locking in mac80211 in Linux allows local users to cause kernel availability loss by triggering a failed access-point start. On the ieee80211_start_ap error path in net/mac80211/cfg.c, the kernel calls ieee80211_vif_release_channel without holding local->mtx, despite its lock assertion. The public reproducer reaches a kernel warning rather than demonstrating data disclosure or code execution.

The record

CVE
CVE-2021-47091
Published
Mar 4, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-667, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 4, 2024CVE 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=295b02c4be74bebf988593b8322369513fcecf68 <87a270625a89fc841f1a7e21aae6176543d8385c
  2. Affected versionversion=295b02c4be74bebf988593b8322369513fcecf68 <ac61b9c6c0549aaeb98194cf429d93c41bfe5f79
  3. Affected versionversion=295b02c4be74bebf988593b8322369513fcecf68 <c1d1ec4db5f7264cfc21993e59e8f2dcecf4b44f
  4. Affected versionversion=5.10

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=295b02c4be74bebf988593b8322369513fcecf68 <87a270625a89fc841f1a7e21aae6176543d8385c; version=295b02c4be74bebf988593b8322369513fcecf68 <ac61b9c6c0549aaeb98194cf429d93c41bfe5f79; version=295b02c4be74bebf988593b8322369513fcecf68 <c1d1ec4db5f7264cfc21993e59e8f2dcecf4b44f; version=5.10

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 exploitPublished

Weakness, pattern, technique

CWE-667Improper Locking
T1499Endpoint Denial of Service

Public exploit references

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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