CVE-2021-47237

Kernel memory exhaustion via unreleased MKISS netdevice

Published May 21, 2024 · Updated May 11, 2026

Resource-management error in Linux allows local users to exhaust kernel memory through repeated opening and closing of the MKISS line discipline. mkiss_open allocates and registers a network device, but mkiss_close unregisters it without calling free_netdev, leaking the device and related allocations. Reaching the flaw requires local low-privileged ioctl access to change a TTY line discipline; repeated cycles consume kernel memory and degrade availability.

CVSS severity5.5
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource-management error in Linux allows local users to exhaust kernel memory through repeated opening and closing of the MKISS line discipline. mkiss_open allocates and registers a network device, but mkiss_close unregisters it without calling free_netdev, leaking the device and related allocations. Reaching the flaw requires local low-privileged ioctl access to change a TTY line discipline; repeated cycles consume kernel memory and degrade availability.

The record

CVE
CVE-2021-47237
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-401, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 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=2.6.14
  2. Affected versionversion=815f62bf742718458ba822a7e1f51f285eb997f2 <290b0b6432e2599021db0b8d6046f756d931c29f
  3. Affected versionversion=815f62bf742718458ba822a7e1f51f285eb997f2 <3942d0f9ace1a95a74930b5b4fc0e5005c62b37b
  4. Affected versionversion=815f62bf742718458ba822a7e1f51f285eb997f2 <765a8a04f828db7222b36a42b1031f576bfe95c3
  5. Affected versionversion=815f62bf742718458ba822a7e1f51f285eb997f2 <7edcc682301492380fbdd604b4516af5ae667a13
  6. Affected versionversion=815f62bf742718458ba822a7e1f51f285eb997f2 <a49cbb762ef20655f5c91abdc13658b0af5e159d
  7. Affected versionversion=815f62bf742718458ba822a7e1f51f285eb997f2 <c16c4716a1b5ba4f83c7e00da457cba06761f119
  8. Affected versionversion=815f62bf742718458ba822a7e1f51f285eb997f2 <c634ba0b4159838ff45a60d3a0ace3b4118077a5
  9. Affected versionversion=815f62bf742718458ba822a7e1f51f285eb997f2 <f4de2b43d13b7cf3ced9310e371b90c836dbd7cd

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.14; version=815f62bf742718458ba822a7e1f51f285eb997f2 <290b0b6432e2599021db0b8d6046f756d931c29f; version=815f62bf742718458ba822a7e1f51f285eb997f2 <3942d0f9ace1a95a74930b5b4fc0e5005c62b37b; version=815f62bf742718458ba822a7e1f51f285eb997f2 <765a8a04f828db7222b36a42b1031f576bfe95c3; version=815f62bf742718458ba822a7e1f51f285eb997f2 <7edcc682301492380fbdd604b4516af5ae667a13; version=815f62bf742718458ba822a7e1f51f285eb997f2 <a49cbb762ef20655f5c91abdc13658b0af5e159d; version=815f62bf742718458ba822a7e1f51f285eb997f2 <c16c4716a1b5ba4f83c7e00da457cba06761f119; version=815f62bf742718458ba822a7e1f51f285eb997f2 <c634ba0b4159838ff45a60d3a0ace3b4118077a5; version=815f62bf742718458ba822a7e1f51f285eb997f2 <f4de2b43d13b7cf3ced9310e371b90c836dbd7cd

Published CVSS scores

5.5CanonicalCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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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