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Full vulnerability report · 2024
CVE-2021-47294High confidence

netrom: Decrease sock refcount when sock timers expire

Linux · Linux

5.5MediumCVSS 3.1
Recommended action
Scheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
Distribution package intelligence

Ubuntu vendor package status

Canonical’s release and source-package findings are shown separately from local repository availability.

1 package state
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Ubuntu releaseSource packageVendor stateFixed versionEvidence
Ubuntu 24.04 LTSnoble · standard archivelinux-raspi-realtimeAffected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition.Not published in this feedCanonical record ↗Source updated 9 Sept 2026
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2021-34299

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionScheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
01

What, why and how

In the Linux kernel, the following vulnerability has been resolved: netrom: Decrease sock refcount when sock timers expire Commit 63346650c1a9 ("netrom: switch to sock timer API") switched to use sock timer API. It replaces mod_timer() by sk_reset_timer(), and del_timer() by sk_stop_timer(). Function sk_reset_timer() will increase the refcount of sock if it is called on an inactive timer, hence, in case the timer expires, we need to decrease the refcount ourselves in the handler, otherwise, the sock refcount will be unbalanced and the sock will never be freed.

What

In the Linux kernel, the following vulnerability has been resolved: netrom: Decrease sock refcount when sock timers expire Commit 63346650c1a9 ("netrom: switch to sock timer API") switched to use sock timer API. It replaces mod_timer() by sk_reset_timer(), and del_timer() by sk_stop_timer(). Function sk_reset_timer() will increase the refcount of sock if it is called on an inactive timer, hence, in case the timer expires, we need to decrease the refcount ourselves in the handler, otherwise, the sock refcount will be unbalanced and the sock will never be freed.

Why

The product uses, accesses, or otherwise operates on a resource after that resource has been expired, released, or revoked.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

In the Linux kernel, the following vulnerability has been resolved: netrom: Decrease sock refcount when sock timers expire Commit 63346650c1a9 ("netrom: switch to sock timer API") switched to use sock timer API. It replaces mod_timer() by sk_reset_timer(), and del_timer() by sk_stop_timer(). Function sk_reset_timer() will increase the refcount of sock if it is called on an inactive timer, hence, in case the timer expires, we need to decrease the refcount ourselves in the handler, otherwise, the sock refcount will be unbalanced and the sock will never be freed.

Why

The product uses, accesses, or otherwise operates on a resource after that resource has been expired, released, or revoked.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
local access → Operation on a Resource after Expiration or Release → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Local
Privileges required
Low: a basic authenticated account is required
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-672

CWE-672: Operation on a Resource after Expiration or Release. The product uses, accesses, or otherwise operates on a resource after that resource has been expired, released, or revoked.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
CWE-672
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

CERT-FR · French · CERTFR-2025-AVI-1008Multiples vulnérabilités dans le noyau Linux d'Ubuntu

/security/notices/USN-7860-5 Bulletin de sécurité Ubuntu USN-7862-2 du 10 novembre 2025 https://ubuntu.com/security/notices/USN-7862-2 Bulletin de sécurité Ubuntu USN-7865-1 du 10 novembre 2025 https://ubuntu.com/security/notices/USN-7865-1 Bulletin de sécurité Ubuntu USN-7835-6 du 12 novembre 2025 https://ubuntu.com/security/notices/USN-7835-6 Bulletin de sécurité Ubuntu USN-7861-3 du 13 novembre 2025 https://ubuntu.com/security/notices/USN-7861-3 Bulletin de sécurité Ubuntu USN-7862-3 du 13 novembre 2025 https://ubuntu.com/security/notices/USN-7862-3 Référence CVE CVE-2021-47149 https://www.cve.org/CVERecord?id=CVE-2021-47149 Référence CVE CVE-2021-47294 https://www.cve.org/CVERecord?id=CVE-2021-47294 Référence CVE CVE-2021-47319 https://www.cve.org/CVERecord?id=CVE-2021-47319 Référence CVE CVE-2021-47330 https://www.cve.org/CVERecord?id=CVE-2021-47330 Référence CVE CVE-2021-47589 https://www.cve.org/CVERecord?id=CVE-2021-47589 Référence CVE CVE-2023-52574 https://www.cve.org/CVERecord?id=CVE-2023-52574 Référence CVE CVE-2023-52650 https://www.cve.org/CVERecord?id=CVE-2023-52650 Référence CVE CVE-2023-53034 https://www.cve.org/CVERecord?id=CVE-2023-53034 Référence CVE CVE-2024-27078 https://www.cve.org/CVERecord?id=CVE-2024-27078 Référence CVE CVE-2024-35849 https://www.cve.org/CVERecord?id=

Official advisory
CERT-FR · French · CERTFR-2025-AVI-0977Multiples vulnérabilités dans le noyau Linux d'Ubuntu

Bulletin de sécurité Ubuntu USN-7863-1 du 06 novembre 2025 https://ubuntu.com/security/notices/USN-7863-1 Bulletin de sécurité Ubuntu USN-7795-5 du 07 novembre 2025 https://ubuntu.com/security/notices/USN-7795-5 Bulletin de sécurité Ubuntu USN-7860-3 du 07 novembre 2025 https://ubuntu.com/security/notices/USN-7860-3 Bulletin de sécurité Ubuntu USN-7860-4 du 07 novembre 2025 https://ubuntu.com/security/notices/USN-7860-4 Bulletin de sécurité Ubuntu USN-7861-2 du 07 novembre 2025 https://ubuntu.com/security/notices/USN-7861-2 Bulletin de sécurité Ubuntu USN-7864-1 du 07 novembre 2025 https://ubuntu.com/security/notices/USN-7864-1 Référence CVE CVE-2021-47294 https://www.cve.org/CVERecord?id=CVE-2021-47294 Référence CVE CVE-2021-47330 https://www.cve.org/CVERecord?id=CVE-2021-47330 Référence CVE CVE-2023-52574 https://www.cve.org/CVERecord?id=CVE-2023-52574 Référence CVE CVE-2023-52593 https://www.cve.org/CVERecord?id=CVE-2023-52593 Référence CVE CVE-2023-52650 https://www.cve.org/CVERecord?id=CVE-2023-52650 Référence CVE CVE-2023-53034 https://www.cve.org/CVERecord?id=CVE-2023-53034 Référence CVE CVE-2024-26700 https://www.cve.org/CVERecord?id=CVE-2024-26700 Référence CVE CVE-2024-26896 https://www.cve.org/CVERecord?id=CVE-2024-26896 Référence CVE CVE-2024-36350 https://www.cve.org/CVERecord?id=

Official advisory
CERT-FR · French · CERTFR-2024-AVI-0610Multiples vulnérabilités dans le noyau Linux de SUSE

d?id=CVE-2021-47103 Référence CVE CVE-2021-47145 https://www.cve.org/CVERecord?id=CVE-2021-47145 Référence CVE CVE-2021-47191 https://www.cve.org/CVERecord?id=CVE-2021-47191 Référence CVE CVE-2021-47193 https://www.cve.org/CVERecord?id=CVE-2021-47193 Référence CVE CVE-2021-47201 https://www.cve.org/CVERecord?id=CVE-2021-47201 Référence CVE CVE-2021-47267 https://www.cve.org/CVERecord?id=CVE-2021-47267 Référence CVE CVE-2021-47270 https://www.cve.org/CVERecord?id=CVE-2021-47270 Référence CVE CVE-2021-47275 https://www.cve.org/CVERecord?id=CVE-2021-47275 Référence CVE CVE-2021-47293 https://www.cve.org/CVERecord?id=CVE-2021-47293 Référence CVE CVE-2021-47294 https://www.cve.org/CVERecord?id=CVE-2021-47294 Référence CVE CVE-2021-47297 https://www.cve.org/CVERecord?id=CVE-2021-47297 Référence CVE CVE-2021-47309 https://www.cve.org/CVERecord?id=CVE-2021-47309 Référence CVE CVE-2021-47328 https://www.cve.org/CVERecord?id=CVE-2021-47328 Référence CVE CVE-2021-47354 https://www.cve.org/CVERecord?id=CVE-2021-47354 Référence CVE CVE-2021-47372 https://www.cve.org/CVERecord?id=CVE-2021-47372 Référence CVE CVE-2021-47379 https://www.cve.org/CVERecord?id=CVE-2021-47379 Référence CVE CVE-2021-47383 https://www.cve.org/CVERecord?id=CVE-2021-47383 Référence CVE CVE-2021-47407 https://www.cve.org/CVERecord?id=

Official advisory
CERT-FR · French · CERTFR-2024-AVI-0578Multiples vulnérabilités dans le noyau Linux de SUSE

d?id=CVE-2021-46955 Référence CVE CVE-2021-47089 https://www.cve.org/CVERecord?id=CVE-2021-47089 Référence CVE CVE-2021-47103 https://www.cve.org/CVERecord?id=CVE-2021-47103 Référence CVE CVE-2021-47191 https://www.cve.org/CVERecord?id=CVE-2021-47191 Référence CVE CVE-2021-47193 https://www.cve.org/CVERecord?id=CVE-2021-47193 Référence CVE CVE-2021-47247 https://www.cve.org/CVERecord?id=CVE-2021-47247 Référence CVE CVE-2021-47267 https://www.cve.org/CVERecord?id=CVE-2021-47267 Référence CVE CVE-2021-47270 https://www.cve.org/CVERecord?id=CVE-2021-47270 Référence CVE CVE-2021-47293 https://www.cve.org/CVERecord?id=CVE-2021-47293 Référence CVE CVE-2021-47294 https://www.cve.org/CVERecord?id=CVE-2021-47294 Référence CVE CVE-2021-47297 https://www.cve.org/CVERecord?id=CVE-2021-47297 Référence CVE CVE-2021-47309 https://www.cve.org/CVERecord?id=CVE-2021-47309 Référence CVE CVE-2021-47311 https://www.cve.org/CVERecord?id=CVE-2021-47311 Référence CVE CVE-2021-47328 https://www.cve.org/CVERecord?id=CVE-2021-47328 Référence CVE CVE-2021-47354 https://www.cve.org/CVERecord?id=CVE-2021-47354 Référence CVE CVE-2021-47368 https://www.cve.org/CVERecord?id=CVE-2021-47368 Référence CVE CVE-2021-47372 https://www.cve.org/CVERecord?id=CVE-2021-47372 Référence CVE CVE-2021-47379 https://www.cve.org/CVERecord?id=

Official advisory
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
ce29e8a259de767f7210d346ad2b031cb8ab2732 < 853262355518cd1247515b74e83fabf038aa6c29; baa9e32336bf6d0d74a7c3486d2a27feaf57cd5f < a01634bf91f2b6c42583770eb6815fb6d1e251cf; 0adf571fa34b27bd0b97b408cc0f0dc54b72f0eb < 48866fd5c361ea417ed24b43fc2a7dc2f5b060ef; 2c6b572458a9127e8070df13fa7f115c29ab1d92 < 9619cc7d97c3aa8ed3cfd2b8678b74fb6d6c7950; 63346650c1a94a92be61a57416ac88c0a47c4327 < 25df44e90ff5959b5c24ad361b648504a7e39ef3; 63346650c1a94a92be61a57416ac88c0a47c4327 < 6811744bd0efb9e472cb15d066cdb460beb8cb8a; 63346650c1a94a92be61a57416ac88c0a47c4327 < bc1660206c3723c37ed4d622ad81781f1e987250; 63346650c1a94a92be61a57416ac88c0a47c4327 < 517a16b1a88bdb6b530f48d5d153478b2552d9a8
Fixed
< 5.0; 4.4.277 ≤ 4.4.*; 4.9.277 ≤ 4.9.*; 4.14.241 ≤ 4.14.*; 4.19.199 ≤ 4.19.*; 5.4.136 ≤ 5.4.*; 5.10.54 ≤ 5.10.*; 5.13.6 ≤ 5.13.*
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 21 May 2024 · Last source change 23 May 2026, 15:19 UTC · CWE-672 · Operation on a Resource after Expiration or Release

CVE recordCVE.org · 5.2
CVSS sourceNIST NVD
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2021-34299
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceNIST NVD
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates →

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2021-47294 · cve.blacktree.nl