BlackTreeCVE Intelligence
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Full vulnerability report · 2021
CVE-2020-25668High confidence

A flaw was found in Linux Kernel because access to the global variable fg_console is not properly synchronized leading to a use after free in con_font_op

Unknown · Linux Kernel

7.0HighCVSS 3.1
Recommended action
Patch only the product branches with a verified fix

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:High, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • Exploitation requires an existing local or physical foothold with privileges.
  • EPSS is 1.03% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict local access and enforce least privilege on affected hosts.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs Unknown Linux Kernel and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 30 daysRemediation target: Within 180 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Distribution package intelligence

Release-specific package status

Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

5 package states
Package result overrides the generic status

BlackTree has verified remediation for at least one product or source, but the relevant distribution still reports no fixed package for 1 affected package state shown here. Treat those rows as affected with no fix until that distribution publishes a fixed version.

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.

Distribution releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourcelinuxVendor fix publishedDebian records a fixed source-package version for this release.5.9.6-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcelinuxVendor fix publishedDebian records a fixed source-package version for this release.5.9.6-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourcelinuxVendor fix publishedDebian records a fixed source-package version for this release.5.9.6-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcelinuxVendor fix publishedDebian records a fixed source-package version for this release.5.9.6-1Debian Security Tracker ↗Source updated 5 Oct 2026
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 Ubuntu Security ↗Source updated 5 Oct 2026
Optional official sources

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

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

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-2020-18330

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 actionPatch only the product branches with a verified fix

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

A flaw was found in Linux Kernel because access to the global variable fg_console is not properly synchronized leading to a use after free in con_font_op.

What

A flaw was found in Linux Kernel because access to the global variable fg_console is not properly synchronized leading to a use after free in con_font_op.

Why

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

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

A flaw was found in Linux Kernel because access to the global variable fg_console is not properly synchronized leading to a use after free in con_font_op.

Why

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

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.
Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path
local access → Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') → 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
High: exploitation depends on specific conditions
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-362 ↗

CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition'). The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

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:H/PR:L/UI:N/S:U/C:H/I:H/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.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.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.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.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-362Public exploit reference
A

Official authority intelligence

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

Cyber Security Agency of Singapore · English · CSA-SB-20210602Security Bulletin 02 Jun 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 02 Jun 2021, published on 2 June 2021. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-920Multiples vulnérabilités dans Android

dans Android. Certaines d'entre elles permettent à un attaquant de provoquer une exécution de code arbitraire à distance, un déni de service et une atteinte à la confidentialité des données. Solution Se référer au bulletin de sécurité de l'éditeur pour l'obtention des correctifs (cf. section Documentation). Documentation Bulletin de sécurité Android 2012-12-01 du 06 décembre 2021 https://source.android.com/security/bulletin/2021-12-01 Bulletin de sécurité Pixel 2012-12-01 du 06 décembre 2021 https://source.android.com/security/bulletin/pixel/2021-12-01 Référence CVE CVE-2020-11263 https://www.cve.org/CVERecord?id=CVE-2020-11263 Référence CVE CVE-2020-25668 https://www.cve.org/CVERecord?id=CVE-2020-25668 Référence CVE CVE-2021-0675 https://www.cve.org/CVERecord?id=CVE-2021-0675 Référence CVE CVE-2021-0704 https://www.cve.org/CVERecord?id=CVE-2021-0704 Référence CVE CVE-2021-0769 https://www.cve.org/CVERecord?id=CVE-2021-0769 Référence CVE CVE-2021-0904 https://www.cve.org/CVERecord?id=CVE-2021-0904 Référence CVE CVE-2021-0952 https://www.cve.org/CVERecord?id=CVE-2021-0952 Référence CVE CVE-2021-0953 https://www.cve.org/CVERecord?id=CVE-2021-0953 Référence CVE CVE-2021-0954 https://www.cve.org/CVERecord?id=CVE-2021-0954 Référence CVE CVE-2021-0955 https://www.cve.org/CVERecord?id=CVE-2021-0955 R

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-149Multiples vulnérabilités dans le noyau Linux d'Ubuntu

d?id=CVE-2020-14314 Référence CVE CVE-2020-15436 https://www.cve.org/CVERecord?id=CVE-2020-15436 Référence CVE CVE-2020-15437 https://www.cve.org/CVERecord?id=CVE-2020-15437 Référence CVE CVE-2020-24490 https://www.cve.org/CVERecord?id=CVE-2020-24490 Référence CVE CVE-2020-25212 https://www.cve.org/CVERecord?id=CVE-2020-25212 Référence CVE CVE-2020-25284 https://www.cve.org/CVERecord?id=CVE-2020-25284 Référence CVE CVE-2020-25641 https://www.cve.org/CVERecord?id=CVE-2020-25641 Référence CVE CVE-2020-25643 https://www.cve.org/CVERecord?id=CVE-2020-25643 Référence CVE CVE-2020-25656 https://www.cve.org/CVERecord?id=CVE-2020-25656 Référence CVE CVE-2020-25668 https://www.cve.org/CVERecord?id=CVE-2020-25668 Référence CVE CVE-2020-25669 https://www.cve.org/CVERecord?id=CVE-2020-25669 Référence CVE CVE-2020-25704 https://www.cve.org/CVERecord?id=CVE-2020-25704 Référence CVE CVE-2020-27152 https://www.cve.org/CVERecord?id=CVE-2020-27152 Référence CVE CVE-2020-27673 https://www.cve.org/CVERecord?id=CVE-2020-27673 Référence CVE CVE-2020-27675 https://www.cve.org/CVERecord?id=CVE-2020-27675 Référence CVE CVE-2020-27777 https://www.cve.org/CVERecord?id=CVE-2020-27777 Référence CVE CVE-2020-27815 https://www.cve.org/CVERecord?id=CVE-2020-27815 Référence CVE CVE-2020-27830 https://www.cve.org/CVERecord?id=

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-125Multiples vulnérabilités dans le noyau Linux de SUSE

d?id=CVE-2020-14381 Référence CVE CVE-2020-14390 https://www.cve.org/CVERecord?id=CVE-2020-14390 Référence CVE CVE-2020-15436 https://www.cve.org/CVERecord?id=CVE-2020-15436 Référence CVE CVE-2020-15437 https://www.cve.org/CVERecord?id=CVE-2020-15437 Référence CVE CVE-2020-25211 https://www.cve.org/CVERecord?id=CVE-2020-25211 Référence CVE CVE-2020-25284 https://www.cve.org/CVERecord?id=CVE-2020-25284 Référence CVE CVE-2020-25285 https://www.cve.org/CVERecord?id=CVE-2020-25285 Référence CVE CVE-2020-25643 https://www.cve.org/CVERecord?id=CVE-2020-25643 Référence CVE CVE-2020-25656 https://www.cve.org/CVERecord?id=CVE-2020-25656 Référence CVE CVE-2020-25668 https://www.cve.org/CVERecord?id=CVE-2020-25668 Référence CVE CVE-2020-25669 https://www.cve.org/CVERecord?id=CVE-2020-25669 Référence CVE CVE-2020-27068 https://www.cve.org/CVERecord?id=CVE-2020-27068 Référence CVE CVE-2020-27777 https://www.cve.org/CVERecord?id=CVE-2020-27777 Référence CVE CVE-2020-27786 https://www.cve.org/CVERecord?id=CVE-2020-27786 Référence CVE CVE-2020-28915 https://www.cve.org/CVERecord?id=CVE-2020-28915 Référence CVE CVE-2020-28974 https://www.cve.org/CVERecord?id=CVE-2020-28974 Référence CVE CVE-2020-29660 https://www.cve.org/CVERecord?id=CVE-2020-29660 Référence CVE CVE-2020-29661 https://www.cve.org/CVERecord?id=

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-120Multiples vulnérabilités dans le noyau Linux de SUSE

cord?id=CVE-2020-0465 Référence CVE CVE-2020-0466 https://www.cve.org/CVERecord?id=CVE-2020-0466 Référence CVE CVE-2020-10781 https://www.cve.org/CVERecord?id=CVE-2020-10781 Référence CVE CVE-2020-11668 https://www.cve.org/CVERecord?id=CVE-2020-11668 Référence CVE CVE-2020-15436 https://www.cve.org/CVERecord?id=CVE-2020-15436 Référence CVE CVE-2020-15437 https://www.cve.org/CVERecord?id=CVE-2020-15437 Référence CVE CVE-2020-25211 https://www.cve.org/CVERecord?id=CVE-2020-25211 Référence CVE CVE-2020-25285 https://www.cve.org/CVERecord?id=CVE-2020-25285 Référence CVE CVE-2020-25639 https://www.cve.org/CVERecord?id=CVE-2020-25639 Référence CVE CVE-2020-25668 https://www.cve.org/CVERecord?id=CVE-2020-25668 Référence CVE CVE-2020-25669 https://www.cve.org/CVERecord?id=CVE-2020-25669 Référence CVE CVE-2020-27068 https://www.cve.org/CVERecord?id=CVE-2020-27068 Référence CVE CVE-2020-27673 https://www.cve.org/CVERecord?id=CVE-2020-27673 Référence CVE CVE-2020-27777 https://www.cve.org/CVERecord?id=CVE-2020-27777 Référence CVE CVE-2020-27786 https://www.cve.org/CVERecord?id=CVE-2020-27786 Référence CVE CVE-2020-27825 https://www.cve.org/CVERecord?id=CVE-2020-27825 Référence CVE CVE-2020-27835 https://www.cve.org/CVERecord?id=CVE-2020-27835 Référence CVE CVE-2020-28374 https://www.cve.org/CVERecord?id=

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-006Multiples vulnérabilités dans le noyau Linux d'Ubuntu

De multiples vulnérabilités ont été découvertes dans le noyau Linux d'Ubuntu. Certaines d'entre elles permettent à un attaquant de provoquer une exécution de code arbitraire, un déni de service et un contournement de la politique de sécurité.

Official advisory ↗
CERT-FR · French · CERTFR-2020-AVI-834Multiples vulnérabilités dans le noyau Linux de Debian LTS

De multiples vulnérabilités ont été découvertes dans le noyau Linux de Debian LTS. Certaines d'entre elles permettent à un attaquant de provoquer un problème de sécurité non spécifié par l'éditeur, un déni de service et une atteinte à l'intégrité des données.

Official advisory ↗
CERT-FR · French · CERTFR-2020-AVI-820Multiples vulnérabilités dans le noyau Linux de SUSE

De multiples vulnérabilités ont été découvertes dans le noyau Linux de SUSE. Certaines d'entre elles permettent à un attaquant de provoquer un problème de sécurité non spécifié par l'éditeur, un déni de service et une atteinte à l'intégrité des données.

Official advisory ↗
CERT-FR · French · CERTFR-2020-AVI-811Multiples vulnérabilités dans le noyau Linux de SUSE

De multiples vulnérabilités ont été découvertes dans le noyau Linux de SUSE. Certaines d'entre elles permettent à un attaquant de provoquer un problème de sécurité non spécifié par l'éditeur, un déni de service et une atteinte à la confidentialité des données.

Official advisory ↗
CERT-FR · French · CERTFR-2020-AVI-794Multiples vulnérabilités dans le noyau Linux de SUSE

De multiples vulnérabilités ont été découvertes dans le noyau Linux de SUSE. Certaines d'entre elles permettent à un attaquant de provoquer un problème de sécurité non spécifié par l'éditeur, une atteinte à l'intégrité des données et une atteinte à la confidentialité des données.

Official advisory ↗
CERT-FR · French · CERTFR-2020-AVI-784Multiples vulnérabilités dans le noyau Linux de SUSE

ord?id=CVE-2020-16120 Référence CVE CVE-2020-2521 https://www.cve.org/CVERecord?id=CVE-2020-2521 Référence CVE CVE-2020-25212 https://www.cve.org/CVERecord?id=CVE-2020-25212 Référence CVE CVE-2020-25284 https://www.cve.org/CVERecord?id=CVE-2020-25284 Référence CVE CVE-2020-25285 https://www.cve.org/CVERecord?id=CVE-2020-25285 Référence CVE CVE-2020-25641 https://www.cve.org/CVERecord?id=CVE-2020-25641 Référence CVE CVE-2020-25643 https://www.cve.org/CVERecord?id=CVE-2020-25643 Référence CVE CVE-2020-25645 https://www.cve.org/CVERecord?id=CVE-2020-25645 Référence CVE CVE-2020-25656 https://www.cve.org/CVERecord?id=CVE-2020-25656 Référence CVE CVE-2020-25668 https://www.cve.org/CVERecord?id=CVE-2020-25668 Référence CVE CVE-2020-25704 https://www.cve.org/CVERecord?id=CVE-2020-25704 Référence CVE CVE-2020-25705 https://www.cve.org/CVERecord?id=CVE-2020-25705 Référence CVE CVE-2020-26088 https://www.cve.org/CVERecord?id=CVE-2020-26088 Référence CVE CVE-2020-27673 https://www.cve.org/CVERecord?id=CVE-2020-27673 Référence CVE CVE-2020-27675 https://www.cve.org/CVERecord?id=CVE-2020-27675 Référence CVE CVE-2020-8694 https://www.cve.org/CVERecord?id=CVE-2020-8694 Gestion détaillée du document le 01 décembre 2020 Version initiale Alertes Avis Bulletins d’actualités Mentions légales Conditions générales

Official advisory ↗
CERT-FR · French · CERTFR-2020-AVI-776Multiples vulnérabilités dans le noyau Linux de SUSE

d?id=CVE-2020-16120 Référence CVE CVE-2020-24490 https://www.cve.org/CVERecord?id=CVE-2020-24490 Référence CVE CVE-2020-25212 https://www.cve.org/CVERecord?id=CVE-2020-25212 Référence CVE CVE-2020-25284 https://www.cve.org/CVERecord?id=CVE-2020-25284 Référence CVE CVE-2020-25285 https://www.cve.org/CVERecord?id=CVE-2020-25285 Référence CVE CVE-2020-25641 https://www.cve.org/CVERecord?id=CVE-2020-25641 Référence CVE CVE-2020-25643 https://www.cve.org/CVERecord?id=CVE-2020-25643 Référence CVE CVE-2020-25645 https://www.cve.org/CVERecord?id=CVE-2020-25645 Référence CVE CVE-2020-25656 https://www.cve.org/CVERecord?id=CVE-2020-25656 Référence CVE CVE-2020-25668 https://www.cve.org/CVERecord?id=CVE-2020-25668 Référence CVE CVE-2020-25704 https://www.cve.org/CVERecord?id=CVE-2020-25704 Référence CVE CVE-2020-25705 https://www.cve.org/CVERecord?id=CVE-2020-25705 Référence CVE CVE-2020-26088 https://www.cve.org/CVERecord?id=CVE-2020-26088 Référence CVE CVE-2020-28974 https://www.cve.org/CVERecord?id=CVE-2020-28974 Référence CVE CVE-2020-8694 https://www.cve.org/CVERecord?id=CVE-2020-8694 Gestion détaillée du document le 26 novembre 2020 Version initiale Alertes Avis Bulletins d’actualités Mentions légales Conditions générales À propos Contact cyber.gouv.fr service-public.fr legifrance.gouv.fr info.gouv

Official advisory ↗
CERT-FR · French · CERTFR-2020-AVI-769Multiples vulnérabilités dans le noyau Linux de SUSE

De multiples vulnérabilités ont été découvertes dans le noyau Linux de SUSE. Certaines d'entre elles permettent à un attaquant de provoquer un problème de sécurité non spécifié par l'éditeur, un déni de service à distance et une atteinte à l'intégrité des données.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2020-016797Linux Kernel における不適切な同期に関する脆弱性

Linux Kernel には、不適切な同期に関する脆弱性が存在します。

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 availability varies by product
Affected
Linux Kernel: 5.9.2
Fixed
An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 26 May 2021 · Last source change 4 Aug 2024, 15:40 UTC · CWE-362 · Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

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-2020-18330
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD modified after enrichment

Missing structured fields: affected product. Missing data is not evidence of low risk; review the primary advisory.

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-2020-25668 · cve.blacktree.nl