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Full vulnerability report · 2024
CVE-2021-47556High confidence

ethtool: ioctl: fix potential NULL deref in ethtool_set_coalesce()

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
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-2021-34558

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: ethtool: ioctl: fix potential NULL deref in ethtool_set_coalesce() ethtool_set_coalesce() now uses both the .get_coalesce() and .set_coalesce() callbacks. But the check for their availability is buggy, so changing the coalesce settings on a device where the driver provides only _one_ of the callbacks results in a NULL pointer dereference instead of an -EOPNOTSUPP. Fix the condition so that the availability of both callbacks is ensured. This also matches the netlink code. Note that reproducing this requires some effort - it only affects the legacy ioctl path, and needs a specific combination of driver options: - have .get_coalesce() and .coalesce_supported but no .set_coalesce(), or - have .set_coalesce() but no .get_coalesce(). Here eg. ethtool doesn't cause the crash as it first attempts to call ethtool_get_coalesce() and bails out on error.

What

In the Linux kernel, the following vulnerability has been resolved: ethtool: ioctl: fix potential NULL deref in ethtool_set_coalesce() ethtool_set_coalesce() now uses both the .get_coalesce() and .set_coalesce() callbacks. But the check for their availability is buggy, so changing the coalesce settings on a device where the driver provides only _one_ of the callbacks results in a NULL pointer dereference instead of an -EOPNOTSUPP. Fix the condition so that the availability of both callbacks is ensured. This also matches the netlink code. Note that reproducing this requires some effort - it only affects the legacy ioctl path, and needs a specific combination of driver options: - have .get_coalesce() and .coalesce_supported but no .set_coalesce(), or - have .set_coalesce() but no .get_coalesce(). Here eg. ethtool doesn't cause the crash as it first attempts to call ethtool_get_coalesce() and bails out on error.

Why

The product dereferences a pointer that it expects to be valid but is NULL.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.

What

In the Linux kernel, the following vulnerability has been resolved: ethtool: ioctl: fix potential NULL deref in ethtool_set_coalesce() ethtool_set_coalesce() now uses both the .get_coalesce() and .set_coalesce() callbacks. But the check for their availability is buggy, so changing the coalesce settings on a device where the driver provides only _one_ of the callbacks results in a NULL pointer dereference instead of an -EOPNOTSUPP. Fix the condition so that the availability of both callbacks is ensured. This also matches the netlink code. Note that reproducing this requires some effort - it only affects the legacy ioctl path, and needs a specific combination of driver options: - have .get_coalesce() and .coalesce_supported but no .set_coalesce(), or - have .set_coalesce() but no .get_coalesce(). Here eg. ethtool doesn't cause the crash as it first attempts to call ethtool_get_coalesce() and bails out on error.

Why

The product dereferences a pointer that it expects to be valid but is NULL.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.

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 → NULL Pointer Dereference → disrupt the affected service
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-476

CWE-476: NULL Pointer Dereference. The product dereferences a pointer that it expects to be valid but is NULL.

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.
Denial of serviceCWE-476
A

Official authority intelligence

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

BSI · German · WID-SEC-W-2024-1235Linux Kernel: Mehrere Schwachstellen ermöglichen Denial of Service und unspezifische Angriffe

Ein lokaler Angreifer kann mehrere Schwachstellen im Linux-Kernel ausnutzen, um einen Denial-of-Service-Zustand zu erzeugen oder unspezifische Angriffe durchzuführen.

Official advisory
CERT-FR · French · CERTFR-2024-AVI-0526Multiples vulnérabilités dans le noyau Linux de SUSE

d?id=CVE-2021-47544 Référence CVE CVE-2021-47548 https://www.cve.org/CVERecord?id=CVE-2021-47548 Référence CVE CVE-2021-47549 https://www.cve.org/CVERecord?id=CVE-2021-47549 Référence CVE CVE-2021-47550 https://www.cve.org/CVERecord?id=CVE-2021-47550 Référence CVE CVE-2021-47551 https://www.cve.org/CVERecord?id=CVE-2021-47551 Référence CVE CVE-2021-47552 https://www.cve.org/CVERecord?id=CVE-2021-47552 Référence CVE CVE-2021-47553 https://www.cve.org/CVERecord?id=CVE-2021-47553 Référence CVE CVE-2021-47554 https://www.cve.org/CVERecord?id=CVE-2021-47554 Référence CVE CVE-2021-47555 https://www.cve.org/CVERecord?id=CVE-2021-47555 Référence CVE CVE-2021-47556 https://www.cve.org/CVERecord?id=CVE-2021-47556 Référence CVE CVE-2021-47557 https://www.cve.org/CVERecord?id=CVE-2021-47557 Référence CVE CVE-2021-47558 https://www.cve.org/CVERecord?id=CVE-2021-47558 Référence CVE CVE-2021-47559 https://www.cve.org/CVERecord?id=CVE-2021-47559 Référence CVE CVE-2021-47560 https://www.cve.org/CVERecord?id=CVE-2021-47560 Référence CVE CVE-2021-47562 https://www.cve.org/CVERecord?id=CVE-2021-47562 Référence CVE CVE-2021-47563 https://www.cve.org/CVERecord?id=CVE-2021-47563 Référence CVE CVE-2021-47564 https://www.cve.org/CVERecord?id=CVE-2021-47564 Référence CVE CVE-2021-47565 https://www.cve.org/CVERecord?id=

Official advisory
CERT-FR · French · CERTFR-2024-AVI-0496Multiples vulnérabilités dans le noyau Linux de SUSE

d?id=CVE-2021-47544 Référence CVE CVE-2021-47548 https://www.cve.org/CVERecord?id=CVE-2021-47548 Référence CVE CVE-2021-47549 https://www.cve.org/CVERecord?id=CVE-2021-47549 Référence CVE CVE-2021-47550 https://www.cve.org/CVERecord?id=CVE-2021-47550 Référence CVE CVE-2021-47551 https://www.cve.org/CVERecord?id=CVE-2021-47551 Référence CVE CVE-2021-47552 https://www.cve.org/CVERecord?id=CVE-2021-47552 Référence CVE CVE-2021-47553 https://www.cve.org/CVERecord?id=CVE-2021-47553 Référence CVE CVE-2021-47554 https://www.cve.org/CVERecord?id=CVE-2021-47554 Référence CVE CVE-2021-47555 https://www.cve.org/CVERecord?id=CVE-2021-47555 Référence CVE CVE-2021-47556 https://www.cve.org/CVERecord?id=CVE-2021-47556 Référence CVE CVE-2021-47557 https://www.cve.org/CVERecord?id=CVE-2021-47557 Référence CVE CVE-2021-47558 https://www.cve.org/CVERecord?id=CVE-2021-47558 Référence CVE CVE-2021-47559 https://www.cve.org/CVERecord?id=CVE-2021-47559 Référence CVE CVE-2021-47560 https://www.cve.org/CVERecord?id=CVE-2021-47560 Référence CVE CVE-2021-47562 https://www.cve.org/CVERecord?id=CVE-2021-47562 Référence CVE CVE-2021-47563 https://www.cve.org/CVERecord?id=CVE-2021-47563 Référence CVE CVE-2021-47564 https://www.cve.org/CVERecord?id=CVE-2021-47564 Référence CVE CVE-2021-47565 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
f3ccfda1931977b80267ba54070a1aeafa18f6ca < abfdd9e2f0f9699015d72317f74154d3e53664e6; f3ccfda1931977b80267ba54070a1aeafa18f6ca < 0276af2176c78771da7f311621a25d7608045827; 5.15
Fixed
< 5.15; 5.15.6 ≤ 5.15.*; 5.16 ≤ *
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 24 May 2024 · Last source change 11 May 2026, 13:56 UTC · CWE-476 · NULL Pointer Dereference

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-2021-34558
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceNIST NVD
NVD statusNVD modified after enrichment

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-2021-47556 · cve.blacktree.nl