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Full vulnerability report · 2021
CVE-2021-38166High confidence

In kernel/bpf/hashtab.c in the Linux kernel through 5.13.8, there is an integer overflow and out-of-bounds write when many elements are placed in a single bucket

Unknown · Unknown

7.8HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Medium, lowered one band.downgradedsince 8 Oct 2026

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • Exploitation requires an existing local or physical foothold with privileges.
  • EPSS is 0.32% 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.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Unknown Unknown 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: As exposure requiresRemediation target: Within 365 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.

Distribution package intelligence

Release-specific package status

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

4 package states
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.5.14.6-1Debian Security Tracker ↗Source updated 23 Oct 2026
Debian bookwormbookworm · sourcelinuxVendor fix publishedDebian records a fixed source-package version for this release.5.14.6-1Debian Security Tracker ↗Source updated 23 Oct 2026
Debian forkyforky · sourcelinuxVendor fix publishedDebian records a fixed source-package version for this release.5.14.6-1Debian Security Tracker ↗Source updated 23 Oct 2026
Debian sidsid · sourcelinuxVendor fix publishedDebian records a fixed source-package version for this release.5.14.6-1Debian Security Tracker ↗Source updated 23 Oct 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2021-38166 · CSAF 2.0 · revision 41 · interimSUSE Product Security TeamCVE-2021-38166
15 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • SLES 15 SP1 CHOST Images for Amazon EC2
  • SLES 15 SP2 CHOST Images for Amazon EC2
  • SLES 15 SP3 CHOST Images for Amazon EC2
  • SLES 15 SP4 CHOST Images for Amazon EC2
  • SLES 15 SP5 CHOST Images for Amazon EC2
  • SLES 15 SP1 CHOST Images for Google
  • SLES 15 SP2 CHOST Images for Google
  • SLES 15 SP3 CHOST Images for Google
  • SLES 15 SP4 CHOST Images for Google
  • SLES 15 SP5 CHOST Images for Google
  • SLES 15 SP1 CHOST Images for Microsoft Azure
  • SLES 15 SP2 CHOST Images for Microsoft Azure
Summary
In kernel/bpf/hashtab.c in the Linux kernel through 5.13.8, there is an integer overflow and out-of-bounds write when many elements are placed in a single bucket. NOTE: exploitation might be impractical without the CAP_SYS_ADMIN capability.
Remediation
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
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-2021-24636

No EUVD known-exploited evidence

In kernel/bpf/hashtab.c in the Linux kernel through 5.13.8, there is an integer overflow and out-of-bounds write when many elements are placed in a single bucket. NOTE: exploitation might be impractical without the CAP_SYS_ADMIN capability.

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
0.0
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

In kernel/bpf/hashtab.c in the Linux kernel through 5.13.8, there is an integer overflow and out-of-bounds write when many elements are placed in a single bucket. NOTE: exploitation might be impractical without the CAP_SYS_ADMIN capability.

What

In kernel/bpf/hashtab.c in the Linux kernel through 5.13.8, there is an integer overflow and out-of-bounds write when many elements are placed in a single bucket. NOTE: exploitation might be impractical without the CAP_SYS_ADMIN capability.

Why

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

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 kernel/bpf/hashtab.c in the Linux kernel through 5.13.8, there is an integer overflow and out-of-bounds write when many elements are placed in a single bucket. NOTE: exploitation might be impractical without the CAP_SYS_ADMIN capability.

Why

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

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 → Integer Overflow or Wraparound → 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-190 ↗

CWE-190: Integer Overflow or Wraparound. The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

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: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.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.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-190
A

Official authority intelligence

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

ENISA EUVD · EUVD-2021-24636Official EUVD mapping

In kernel/bpf/hashtab.c in the Linux kernel through 5.13.8, there is an integer overflow and out-of-bounds write when many elements are placed in a single bucket. NOTE: exploitation might be impractical without the CAP_SYS_ADMIN capability.

Official EUVD record ↗
Cyber Security Agency of Singapore · English · CSA-SB-20210811Security Bulletin 11 Aug 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 11 Aug 2021, published on 11 August 2021. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-814Multiples 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 à distance et un contournement de la politique de sécurité.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-798Multiples 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 une atteinte à la confidentialité des données.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-785Multiples vulnérabilités dans le noyau Linux de SUSE

ve.org/CVERecord?id=CVE-2021-3732 Référence CVE CVE-2021-3739 https://www.cve.org/CVERecord?id=CVE-2021-3739 Référence CVE CVE-2021-3743 https://www.cve.org/CVERecord?id=CVE-2021-3743 Référence CVE CVE-2021-3744 https://www.cve.org/CVERecord?id=CVE-2021-3744 Référence CVE CVE-2021-3752 https://www.cve.org/CVERecord?id=CVE-2021-3752 Référence CVE CVE-2021-3753 https://www.cve.org/CVERecord?id=CVE-2021-3753 Référence CVE CVE-2021-3759 https://www.cve.org/CVERecord?id=CVE-2021-3759 Référence CVE CVE-2021-3764 https://www.cve.org/CVERecord?id=CVE-2021-3764 Référence CVE CVE-2021-38160 https://www.cve.org/CVERecord?id=CVE-2021-38160 Référence CVE CVE-2021-38166 https://www.cve.org/CVERecord?id=CVE-2021-38166 Référence CVE CVE-2021-38198 https://www.cve.org/CVERecord?id=CVE-2021-38198 Référence CVE CVE-2021-38204 https://www.cve.org/CVERecord?id=CVE-2021-38204 Référence CVE CVE-2021-38205 https://www.cve.org/CVERecord?id=CVE-2021-38205 Référence CVE CVE-2021-38206 https://www.cve.org/CVERecord?id=CVE-2021-38206 Référence CVE CVE-2021-38207 https://www.cve.org/CVERecord?id=CVE-2021-38207 Référence CVE CVE-2021-38209 https://www.cve.org/CVERecord?id=CVE-2021-38209 Référence CVE CVE-2021-40490 https://www.cve.org/CVERecord?id=CVE-2021-40490 Gestion détaillée du document le 14 octobre 2021 Version initi

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-751Multiples vulnérabilités dans Google Android

ecord?id=CVE-2021-30297 Référence CVE CVE-2021-30302 https://www.cve.org/CVERecord?id=CVE-2021-30302 Référence CVE CVE-2021-30305 https://www.cve.org/CVERecord?id=CVE-2021-30305 Référence CVE CVE-2021-30306 https://www.cve.org/CVERecord?id=CVE-2021-30306 Référence CVE CVE-2021-30310 https://www.cve.org/CVERecord?id=CVE-2021-30310 Référence CVE CVE-2021-30312 https://www.cve.org/CVERecord?id=CVE-2021-30312 Référence CVE CVE-2021-31916 https://www.cve.org/CVERecord?id=CVE-2021-31916 Référence CVE CVE-2021-3489 https://www.cve.org/CVERecord?id=CVE-2021-3489 Référence CVE CVE-2021-3490 https://www.cve.org/CVERecord?id=CVE-2021-3490 Référence CVE CVE-2021-38166 https://www.cve.org/CVERecord?id=CVE-2021-38166 Gestion détaillée du document le 05 octobre 2021 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.fr france.fr info.gouv.fr/risques Premier Ministre / Secrétariat Général de la Défense et de la Sécurité Nationale / Agence nationale de la sécurité des systèmes d'information

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-742Multiples 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 à distance, un déni de service à distance et une atteinte à la confidentialité des données.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-737Multiples vulnérabilités dans le noyau linux de Debian

De multiples vulnérabilités ont été découvertes dans le noyau linux de Debian. Certaines d'entre elles permettent à un attaquant de provoquer une exécution de code arbitraire, un déni de service et une atteinte à l'intégrité des données.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-730Multiples vulnérabilités dans le noyau Linux de SUSE

ve.org/CVERecord?id=CVE-2021-3653 Référence CVE CVE-2021-3656 https://www.cve.org/CVERecord?id=CVE-2021-3656 Référence CVE CVE-2021-3679 https://www.cve.org/CVERecord?id=CVE-2021-3679 Référence CVE CVE-2021-3732 https://www.cve.org/CVERecord?id=CVE-2021-3732 Référence CVE CVE-2021-3739 https://www.cve.org/CVERecord?id=CVE-2021-3739 Référence CVE CVE-2021-3743 https://www.cve.org/CVERecord?id=CVE-2021-3743 Référence CVE CVE-2021-3753 https://www.cve.org/CVERecord?id=CVE-2021-3753 Référence CVE CVE-2021-3759 https://www.cve.org/CVERecord?id=CVE-2021-3759 Référence CVE CVE-2021-38160 https://www.cve.org/CVERecord?id=CVE-2021-38160 Référence CVE CVE-2021-38166 https://www.cve.org/CVERecord?id=CVE-2021-38166 Référence CVE CVE-2021-38198 https://www.cve.org/CVERecord?id=CVE-2021-38198 Référence CVE CVE-2021-38204 https://www.cve.org/CVERecord?id=CVE-2021-38204 Référence CVE CVE-2021-38205 https://www.cve.org/CVERecord?id=CVE-2021-38205 Référence CVE CVE-2021-38206 https://www.cve.org/CVERecord?id=CVE-2021-38206 Référence CVE CVE-2021-38207 https://www.cve.org/CVERecord?id=CVE-2021-38207 Référence CVE CVE-2021-38209 https://www.cve.org/CVERecord?id=CVE-2021-38209 Gestion détaillée du document le 24 septembre 2021 Version initiale Alertes Avis Bulletins d’actualités Mentions légales Conditions général

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-727Multiples vulnérabilités dans le noyau Linux de SUSE

ve.org/CVERecord?id=CVE-2021-3653 Référence CVE CVE-2021-3656 https://www.cve.org/CVERecord?id=CVE-2021-3656 Référence CVE CVE-2021-3679 https://www.cve.org/CVERecord?id=CVE-2021-3679 Référence CVE CVE-2021-3732 https://www.cve.org/CVERecord?id=CVE-2021-3732 Référence CVE CVE-2021-3739 https://www.cve.org/CVERecord?id=CVE-2021-3739 Référence CVE CVE-2021-3743 https://www.cve.org/CVERecord?id=CVE-2021-3743 Référence CVE CVE-2021-3753 https://www.cve.org/CVERecord?id=CVE-2021-3753 Référence CVE CVE-2021-3759 https://www.cve.org/CVERecord?id=CVE-2021-3759 Référence CVE CVE-2021-38160 https://www.cve.org/CVERecord?id=CVE-2021-38160 Référence CVE CVE-2021-38166 https://www.cve.org/CVERecord?id=CVE-2021-38166 Référence CVE CVE-2021-38198 https://www.cve.org/CVERecord?id=CVE-2021-38198 Référence CVE CVE-2021-38204 https://www.cve.org/CVERecord?id=CVE-2021-38204 Référence CVE CVE-2021-38205 https://www.cve.org/CVERecord?id=CVE-2021-38205 Référence CVE CVE-2021-38206 https://www.cve.org/CVERecord?id=CVE-2021-38206 Référence CVE CVE-2021-38207 https://www.cve.org/CVERecord?id=CVE-2021-38207 Référence CVE CVE-2021-38209 https://www.cve.org/CVERecord?id=CVE-2021-38209 Gestion détaillée du document le 23 septembre 2021 Version initiale Alertes Avis Bulletins d’actualités Mentions légales Conditions général

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-009554Linux Kernel における境界外書き込みに関する脆弱性

Linux Kernel には、境界外書き込みに関する脆弱性、および整数オーバーフローの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.
Patch available
Affected
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
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 7 Aug 2021 · Last source change 8 Oct 2026, 21:03 UTC · CWE-190 · Integer Overflow or Wraparound

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-2021-24636
Product sourceVendor CSAF · SUSE Product Security Team
Remediation sourceVendor CSAF · SUSE Product Security Team
CWE sourceNIST NVD
NVD statusNVD enriched

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
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2021-24636↗Vendor CSAF · SUSE Product Security Team↗CVE authority or vendor reference↗Patch or update reference↗Official CVE record (CNA and ADP data)↗NVD record↗
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-2021-38166 · cve.blacktree.nl