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Full vulnerability report · 2021
CVE-2020-35503High confidence

A NULL pointer dereference flaw was found in the megasas-gen2 SCSI host bus adapter emulation of QEMU in versions before and including 6.0

n/a · QEMU

6.0MediumCVSS 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.

Fix not verified
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 archiveqemuUnder evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical record ↗Source updated 8 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-2020-23172

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.

Fix not verified
01

What, why and how

A NULL pointer dereference flaw was found in the megasas-gen2 SCSI host bus adapter emulation of QEMU in versions before and including 6.0. This issue occurs in the megasas_command_cancelled() callback function while dropping a SCSI request. This flaw allows a privileged guest user to crash the QEMU process on the host, resulting in a denial of service. The highest threat from this vulnerability is to system availability.

What

A NULL pointer dereference flaw was found in the megasas-gen2 SCSI host bus adapter emulation of QEMU in versions before and including 6.0. This issue occurs in the megasas_command_cancelled() callback function while dropping a SCSI request. This flaw allows a privileged guest user to crash the QEMU process on the host, resulting in a denial of service. The highest threat from this vulnerability is to system availability.

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 elevated privileges. If successful, the issue may disrupt the affected service.

What

A NULL pointer dereference flaw was found in the megasas-gen2 SCSI host bus adapter emulation of QEMU in versions before and including 6.0. This issue occurs in the megasas_command_cancelled() callback function while dropping a SCSI request. This flaw allows a privileged guest user to crash the QEMU process on the host, resulting in a denial of service. The highest threat from this vulnerability is to system availability.

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 elevated 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
High: elevated access is required
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Changed: exploitation can affect a different 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:H/UI:N/S:C/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.PRHighPrivileges required: The attacker needs elevated or administrative privileges.UINoneUser interaction: No action by another user is required.SChangedScope: The attack can affect a component governed by a different security 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-2022-2259QEMU: Mehrere Schwachstellen ermöglichen Denial of Service

Ein lokaler Angreifer kann mehrere Schwachstellen in QEMU ausnutzen, um einen Denial of Service Angriff durchzuführen.

Official advisory
CERT-FR · French · CERTFR-2026-AVI-0326Multiples vulnérabilités dans les produits VMware

d?id=CVE-2020-26140 Référence CVE CVE-2020-26142 https://www.cve.org/CVERecord?id=CVE-2020-26142 Référence CVE CVE-2020-26143 https://www.cve.org/CVERecord?id=CVE-2020-26143 Référence CVE CVE-2020-26146 https://www.cve.org/CVERecord?id=CVE-2020-26146 Référence CVE CVE-2020-26556 https://www.cve.org/CVERecord?id=CVE-2020-26556 Référence CVE CVE-2020-26557 https://www.cve.org/CVERecord?id=CVE-2020-26557 Référence CVE CVE-2020-26559 https://www.cve.org/CVERecord?id=CVE-2020-26559 Référence CVE CVE-2020-26560 https://www.cve.org/CVERecord?id=CVE-2020-26560 Référence CVE CVE-2020-35501 https://www.cve.org/CVERecord?id=CVE-2020-35501 Référence CVE CVE-2020-35503 https://www.cve.org/CVERecord?id=CVE-2020-35503 Référence CVE CVE-2021-0066 https://www.cve.org/CVERecord?id=CVE-2021-0066 Référence CVE CVE-2021-0072 https://www.cve.org/CVERecord?id=CVE-2021-0072 Référence CVE CVE-2021-0076 https://www.cve.org/CVERecord?id=CVE-2021-0076 Référence CVE CVE-2021-0161 https://www.cve.org/CVERecord?id=CVE-2021-0161 Référence CVE CVE-2021-0164 https://www.cve.org/CVERecord?id=CVE-2021-0164 Référence CVE CVE-2021-0165 https://www.cve.org/CVERecord?id=CVE-2021-0165 Référence CVE CVE-2021-0166 https://www.cve.org/CVERecord?id=CVE-2021-0166 Référence CVE CVE-2021-0168 https://www.cve.org/CVERecord?id=CVE-2021-0168 R

Official advisory
CERT-FR · French · CERTFR-2026-AVI-0316Multiples vulnérabilités dans les produits VMware

d?id=CVE-2020-26140 Référence CVE CVE-2020-26142 https://www.cve.org/CVERecord?id=CVE-2020-26142 Référence CVE CVE-2020-26143 https://www.cve.org/CVERecord?id=CVE-2020-26143 Référence CVE CVE-2020-26146 https://www.cve.org/CVERecord?id=CVE-2020-26146 Référence CVE CVE-2020-26556 https://www.cve.org/CVERecord?id=CVE-2020-26556 Référence CVE CVE-2020-26557 https://www.cve.org/CVERecord?id=CVE-2020-26557 Référence CVE CVE-2020-26559 https://www.cve.org/CVERecord?id=CVE-2020-26559 Référence CVE CVE-2020-26560 https://www.cve.org/CVERecord?id=CVE-2020-26560 Référence CVE CVE-2020-35501 https://www.cve.org/CVERecord?id=CVE-2020-35501 Référence CVE CVE-2020-35503 https://www.cve.org/CVERecord?id=CVE-2020-35503 Référence CVE CVE-2021-0066 https://www.cve.org/CVERecord?id=CVE-2021-0066 Référence CVE CVE-2021-0072 https://www.cve.org/CVERecord?id=CVE-2021-0072 Référence CVE CVE-2021-0076 https://www.cve.org/CVERecord?id=CVE-2021-0076 Référence CVE CVE-2021-0161 https://www.cve.org/CVERecord?id=CVE-2021-0161 Référence CVE CVE-2021-0164 https://www.cve.org/CVERecord?id=CVE-2021-0164 Référence CVE CVE-2021-0165 https://www.cve.org/CVERecord?id=CVE-2021-0165 Référence CVE CVE-2021-0166 https://www.cve.org/CVERecord?id=CVE-2021-0166 Référence CVE CVE-2021-0168 https://www.cve.org/CVERecord?id=CVE-2021-0168 R

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.
Fix not verified
Affected
All QEMU versions before and including 6.0
Fixed
No fixed version is explicitly recorded in the structured CVE data.
Action
No verified patch reference is present in the current structured sources. Check the vendor advisory before making a change.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 2 Jun 2021 · Last source change 4 Aug 2024, 17:02 UTC · CWE-476 · NULL Pointer Dereference

CVE recordCVE.org · 5.1
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-2020-23172
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
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-2020-35503 · cve.blacktree.nl