CVE-2021-47021

Local service interruption via unreleased transmit tokens

Published Feb 28, 2024 · Updated May 23, 2026

Memory leak in the Linux kernel mt7915 driver in 5.11.4 through 5.11.20 and 5.12 through 5.12.3 allows local users to interrupt service. The mt7915_unregister_device() teardown frees pending TXWI structures without first calling mt7915_tx_token_put(), leaving transmit-token memory allocated. Triggering requires local low-privileged access and an mt7915 device teardown; published sources do not specify whether exhaustion produces a hang or crash.

CVSS severity5.5
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory leak in the Linux kernel mt7915 driver in 5.11.4 through 5.11.20 and 5.12 through 5.12.3 allows local users to interrupt service. The mt7915_unregister_device() teardown frees pending TXWI structures without first calling mt7915_tx_token_put(), leaving transmit-token memory allocated. Triggering requires local low-privileged access and an mt7915 device teardown; published sources do not specify whether exhaustion produces a hang or crash.

The record

CVE
CVE-2021-47021
Published
Feb 28, 2024
Updated
May 23, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-401, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 28, 2024CVE publishedPublication date reported by the CVE source.
  2. May 23, 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=4e9e896f81932e337a93ad61cd3d9647571c4637 <81483309ce861a9fa7835322787f68a443fea364
  2. Affected versionversion=5.11.4 <5.11.21
  3. Affected versionversion=5.12
  4. Affected versionversion=f285dfb98562e8380101095d168910df1d07d8be <d754c80ae82a662e692a82faad71b8c218cb7f52
  5. Affected versionversion=f285dfb98562e8380101095d168910df1d07d8be <e9d32af478cfc3744a45245c0b126738af4b3ac4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4e9e896f81932e337a93ad61cd3d9647571c4637 <81483309ce861a9fa7835322787f68a443fea364; version=5.11.4 <5.11.21; version=5.12; version=f285dfb98562e8380101095d168910df1d07d8be <d754c80ae82a662e692a82faad71b8c218cb7f52; version=f285dfb98562e8380101095d168910df1d07d8be <e9d32af478cfc3744a45245c0b126738af4b3ac4

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

CWE-401Missing Release of Memory after Effective Lifetime
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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