CVE-2021-47294

Service interruption via NET/ROM socket reference leak

Published May 21, 2024 · Updated May 23, 2026

Resource-management error in affected Linux kernels allows local users to cause a service interrupt by expiring NET/ROM socket timers. In net/netrom/nr_timer.c, sk_reset_timer increments the socket reference count for an inactive timer, but the expiry handlers fail to decrement it, so the socket is never freed. Low-privileged local access and a reachable NET/ROM socket-timer path are required; repeated expirations consume unreleased kernel socket resources.

CVSS severity5.5
Medium
EPSS probability0.28%
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 affected Linux kernels allows local users to cause a service interrupt by expiring NET/ROM socket timers. In net/netrom/nr_timer.c, sk_reset_timer increments the socket reference count for an inactive timer, but the expiry handlers fail to decrement it, so the socket is never freed. Low-privileged local access and a reachable NET/ROM socket-timer path are required; repeated expirations consume unreleased kernel socket resources.

The record

CVE
CVE-2021-47294
Published
May 21, 2024
Updated
May 23, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-672, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 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=0adf571fa34b27bd0b97b408cc0f0dc54b72f0eb <48866fd5c361ea417ed24b43fc2a7dc2f5b060ef
  2. Affected versionversion=2c6b572458a9127e8070df13fa7f115c29ab1d92 <9619cc7d97c3aa8ed3cfd2b8678b74fb6d6c7950
  3. Affected versionversion=3.18.134 <3.19
  4. Affected versionversion=4.14.98 <4.14.241
  5. Affected versionversion=4.19.20 <4.19.199
  6. Affected versionversion=4.20.7 <4.21
  7. Affected versionversion=4.4.173 <4.4.277
  8. Affected versionversion=4.9.155 <4.9.277
  9. Affected versionversion=5.0
  10. Affected versionversion=519e8a22a454b1f1baa3a151b184fe51bc18e178
  11. Affected versionversion=63346650c1a94a92be61a57416ac88c0a47c4327 <25df44e90ff5959b5c24ad361b648504a7e39ef3
  12. Affected versionversion=63346650c1a94a92be61a57416ac88c0a47c4327 <517a16b1a88bdb6b530f48d5d153478b2552d9a8
  13. Affected versionversion=63346650c1a94a92be61a57416ac88c0a47c4327 <6811744bd0efb9e472cb15d066cdb460beb8cb8a
  14. Affected versionversion=63346650c1a94a92be61a57416ac88c0a47c4327 <bc1660206c3723c37ed4d622ad81781f1e987250
  15. Affected versionversion=baa9e32336bf6d0d74a7c3486d2a27feaf57cd5f <a01634bf91f2b6c42583770eb6815fb6d1e251cf
  16. Affected versionversion=ce29e8a259de767f7210d346ad2b031cb8ab2732 <853262355518cd1247515b74e83fabf038aa6c29
  17. Affected versionversion=f1d9a1f2ef6ff17293d21d5e6b80e04bea0cf508

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=0adf571fa34b27bd0b97b408cc0f0dc54b72f0eb <48866fd5c361ea417ed24b43fc2a7dc2f5b060ef; version=2c6b572458a9127e8070df13fa7f115c29ab1d92 <9619cc7d97c3aa8ed3cfd2b8678b74fb6d6c7950; version=3.18.134 <3.19; version=4.14.98 <4.14.241; version=4.19.20 <4.19.199; version=4.20.7 <4.21; version=4.4.173 <4.4.277; version=4.9.155 <4.9.277; version=5.0; version=519e8a22a454b1f1baa3a151b184fe51bc18e178; version=63346650c1a94a92be61a57416ac88c0a47c4327 <25df44e90ff5959b5c24ad361b648504a7e39ef3; version=63346650c1a94a92be61a57416ac88c0a47c4327 <517a16b1a88bdb6b530f48d5d153478b2552d9a8; version=63346650c1a94a92be61a57416ac88c0a47c4327 <6811744bd0efb9e472cb15d066cdb460beb8cb8a; version=63346650c1a94a92be61a57416ac88c0a47c4327 <bc1660206c3723c37ed4d622ad81781f1e987250; version=baa9e32336bf6d0d74a7c3486d2a27feaf57cd5f <a01634bf91f2b6c42583770eb6815fb6d1e251cf; version=ce29e8a259de767f7210d346ad2b031cb8ab2732 <853262355518cd1247515b74e83fabf038aa6c29; version=f1d9a1f2ef6ff17293d21d5e6b80e04bea0cf508

Published CVSS scores

5.5Canonical UbuntuCVSS: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-672Operation on a Resource after Expiration or Release
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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