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Full vulnerability report · 2021
CVE-2021-31440High confidence

This vulnerability allows local attackers to escalate privileges on affected installations of Linux Kernel 5.11.15

Linux · Kernel

7.0HighCVSS 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 3 Aug 2024

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • Exploitation requires an existing local or physical foothold with privileges.
  • EPSS is 1.75% 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 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: 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.5.10.38-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcelinuxVendor fix publishedDebian records a fixed source-package version for this release.5.10.38-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourcelinuxVendor fix publishedDebian records a fixed source-package version for this release.5.10.38-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcelinuxVendor fix publishedDebian records a fixed source-package version for this release.5.10.38-1Debian Security Tracker ↗Source updated 5 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-2021-31440 · CSAF 2.0 · revision 3 · status not statedRed Hat Product Securitykernel: local escalation of privileges in handling of eBPF programs
101 fixed

The vendor explicitly identifies these products or versions as containing the fix.

  • bpftool-0:4.18.0-348.el8.aarch64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
  • bpftool-0:4.18.0-348.el8.ppc64le as a component of Red Hat Enterprise Linux BaseOS (v. 8)
  • bpftool-0:4.18.0-348.el8.s390x as a component of Red Hat Enterprise Linux BaseOS (v. 8)
  • bpftool-0:4.18.0-348.el8.x86_64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
  • bpftool-debuginfo-0:4.18.0-348.el8.aarch64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
  • bpftool-debuginfo-0:4.18.0-348.el8.ppc64le as a component of Red Hat Enterprise Linux BaseOS (v. 8)
  • bpftool-debuginfo-0:4.18.0-348.el8.s390x as a component of Red Hat Enterprise Linux BaseOS (v. 8)
  • bpftool-debuginfo-0:4.18.0-348.el8.x86_64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
  • kernel-0:4.18.0-348.el8.aarch64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
  • kernel-0:4.18.0-348.el8.ppc64le as a component of Red Hat Enterprise Linux BaseOS (v. 8)
  • kernel-0:4.18.0-348.el8.s390x as a component of Red Hat Enterprise Linux BaseOS (v. 8)
  • kernel-0:4.18.0-348.el8.src as a component of Red Hat Enterprise Linux BaseOS (v. 8)
Summary
An out-of-bounds access flaw was found in the Linux kernel’s implementation of the eBPF code verifier, where an incorrect register bounds calculation while checking unsigned 32-bit instructions in an eBPF program occurs.. By default accessing the eBPF verifier is only accessible to privileged users with CAP_SYS_ADMIN. The issue results from the lack of proper validation of user-supplied eBPF programs prior to executing them. A local user could use this flaw to crash the system or possibly escalate their privileges on the system.
Remediation
For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section. Additional Changes: For detailed information on changes in this release, see the Red Hat Enterprise Linux 8.5 Release Notes linked from the References section. For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 The system must be rebooted for this update to take effect.
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-2021-18340

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 actionWithin 7 days

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

Patch available
01

What, why and how

This vulnerability allows local attackers to escalate privileges on affected installations of Linux Kernel 5.11.15. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the handling of eBPF programs. The issue results from the lack of proper validation of user-supplied eBPF programs prior to executing them. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of the kernel. Was ZDI-CAN-13661.

What

This vulnerability allows local attackers to escalate privileges on affected installations of Linux Kernel 5.11.15. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the handling of eBPF programs. The issue results from the lack of proper validation of user-supplied eBPF programs prior to executing them. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of the kernel. Was ZDI-CAN-13661.

Why

The product performs a calculation that generates incorrect or unintended results that are later used in security-critical decisions or resource management.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may execute code or commands in the affected security context.

What

This vulnerability allows local attackers to escalate privileges on affected installations of Linux Kernel 5.11.15. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the handling of eBPF programs. The issue results from the lack of proper validation of user-supplied eBPF programs prior to executing them. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of the kernel. Was ZDI-CAN-13661.

Why

The product performs a calculation that generates incorrect or unintended results that are later used in security-critical decisions or resource management.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may execute code or commands in the affected security context.

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 → Incorrect Calculation → execute code or commands in the affected security context
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-682 ↗

CWE-682: Incorrect Calculation. The product performs a calculation that generates incorrect or unintended results that are later used in security-critical decisions or resource management.

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
After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
Remote code executionCWE-682
A

Official authority intelligence

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

BSI · German · WID-SEC-2022-0137Android Patchday Juni 2022

Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Google Android ausnutzen, um seine Privilegien zu erhöhen, vertrauliche Informationen offenzulegen, beliebigen Code auszuführen und einen Denial-of-Service-Zustand auszulösen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20210526Security Bulletin 26 May 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 26 May 2021, published on 26 May 2021. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-864Multiples vulnérabilités dans le noyau Linux de Red Hat

rd?id=CVE-2021-0129 Référence CVE CVE-2021-20194 https://www.cve.org/CVERecord?id=CVE-2021-20194 Référence CVE CVE-2021-20239 https://www.cve.org/CVERecord?id=CVE-2021-20239 Référence CVE CVE-2021-23133 https://www.cve.org/CVERecord?id=CVE-2021-23133 Référence CVE CVE-2021-28950 https://www.cve.org/CVERecord?id=CVE-2021-28950 Référence CVE CVE-2021-28971 https://www.cve.org/CVERecord?id=CVE-2021-28971 Référence CVE CVE-2021-29155 https://www.cve.org/CVERecord?id=CVE-2021-29155 Référence CVE CVE-2021-29646 https://www.cve.org/CVERecord?id=CVE-2021-29646 Référence CVE CVE-2021-29650 https://www.cve.org/CVERecord?id=CVE-2021-29650 Référence CVE CVE-2021-31440 https://www.cve.org/CVERecord?id=CVE-2021-31440 Référence CVE CVE-2021-31829 https://www.cve.org/CVERecord?id=CVE-2021-31829 Référence CVE CVE-2021-31916 https://www.cve.org/CVERecord?id=CVE-2021-31916 Référence CVE CVE-2021-33200 https://www.cve.org/CVERecord?id=CVE-2021-33200 Référence CVE CVE-2021-3348 https://www.cve.org/CVERecord?id=CVE-2021-3348 Référence CVE CVE-2021-3489 https://www.cve.org/CVERecord?id=CVE-2021-3489 Référence CVE CVE-2021-3564 https://www.cve.org/CVERecord?id=CVE-2021-3564 Référence CVE CVE-2021-3573 https://www.cve.org/CVERecord?id=CVE-2021-3573 Référence CVE CVE-2021-3600 https://www.cve.org/CVERecord?id=CVE-2021-

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

s://www.suse.com/support/update/announcement/2021/suse-su-20213388-1/ Bulletin de sécurité SUSE suse-su-20213389-1 du 13 octobre 2021 https://www.suse.com/support/update/announcement/2021/suse-su-20213389-1/ Bulletin de sécurité SUSE suse-su-20213401-1 du 13 octobre 2021 https://www.suse.com/support/update/announcement/2021/suse-su-20213401-1/ Bulletin de sécurité SUSE suse-su-20213415-1 du 14 octobre 2021 https://www.suse.com/support/update/announcement/2021/suse-su-20213415-1/ Référence CVE CVE-2020-12770 https://www.cve.org/CVERecord?id=CVE-2020-12770 Référence CVE CVE-2020-3702 https://www.cve.org/CVERecord?id=CVE-2020-3702 Référence CVE CVE-2021-31440 https://www.cve.org/CVERecord?id=CVE-2021-31440 Référence CVE CVE-2021-34556 https://www.cve.org/CVERecord?id=CVE-2021-34556 Référence CVE CVE-2021-35477 https://www.cve.org/CVERecord?id=CVE-2021-35477 Référence CVE CVE-2021-3573 https://www.cve.org/CVERecord?id=CVE-2021-3573 Référence CVE CVE-2021-3640 https://www.cve.org/CVERecord?id=CVE-2021-3640 Référence CVE CVE-2021-3653 https://www.cve.org/CVERecord?id=CVE-2021-3653 Référence CVE CVE-2021-3656 https://www.cve.org/CVERecord?id=CVE-2021-3656 Référence CVE CVE-2021-3669 https://www.cve.org/CVERecord?id=CVE-2021-3669 Référence CVE CVE-2021-3679 https://www.cve.org/CVERecord?id=CVE-2021-36

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-492Multiples 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 l'intégrité des données.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-483Multiples vulnérabilités dans le noyau Linux d'Ubuntu

d?id=CVE-2020-25672 Référence CVE CVE-2020-25673 https://www.cve.org/CVERecord?id=CVE-2020-25673 Référence CVE CVE-2020-26139 https://www.cve.org/CVERecord?id=CVE-2020-26139 Référence CVE CVE-2020-26141 https://www.cve.org/CVERecord?id=CVE-2020-26141 Référence CVE CVE-2020-26145 https://www.cve.org/CVERecord?id=CVE-2020-26145 Référence CVE CVE-2020-26147 https://www.cve.org/CVERecord?id=CVE-2020-26147 Référence CVE CVE-2021-23133 https://www.cve.org/CVERecord?id=CVE-2021-23133 Référence CVE CVE-2021-23134 https://www.cve.org/CVERecord?id=CVE-2021-23134 Référence CVE CVE-2021-29155 https://www.cve.org/CVERecord?id=CVE-2021-29155 Référence CVE CVE-2021-31440 https://www.cve.org/CVERecord?id=CVE-2021-31440 Référence CVE CVE-2021-31829 https://www.cve.org/CVERecord?id=CVE-2021-31829 Référence CVE CVE-2021-32399 https://www.cve.org/CVERecord?id=CVE-2021-32399 Référence CVE CVE-2021-33034 https://www.cve.org/CVERecord?id=CVE-2021-33034 Référence CVE CVE-2021-33200 https://www.cve.org/CVERecord?id=CVE-2021-33200 Référence CVE CVE-2021-3506 https://www.cve.org/CVERecord?id=CVE-2021-3506 Référence CVE CVE-2021-3543 https://www.cve.org/CVERecord?id=CVE-2021-3543 Référence CVE CVE-2021-3600 https://www.cve.org/CVERecord?id=CVE-2021-3600 Référence CVE CVE-2021-3609 https://www.cve.org/CVERecord?id=CVE-202

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-007250Linux Kernel における計算の誤りに関する脆弱性

Linux Kernel には、計算の誤りに関する脆弱性が存在します。 Zero Day Initiative は、本脆弱性に ZDI-CAN-13661 を採番していました。

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
Kernel: 5.11.15
Fixed
Action
For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section. Additional Changes: For detailed information on changes in this release, see the Red Hat Enterprise Linux 8.5 Release Notes linked from the References section. For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 The system must be rebooted for this update to take effect.
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 2021 · Last source change 3 Aug 2024, 22:55 UTC · CWE-682 · Incorrect Calculation

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-2021-18340
Product sourceCNA
Remediation sourceVendor CSAF · Red Hat Product Security
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 ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    5.11.15 · 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.
    After
    5.11.15 · Fixed: For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section. Additional Changes: For detailed information on changes in this release, see the Red Hat Enterprise Linux 8.5 Release Notes linked from the References section. For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 The system must be rebooted for this update to take effect.
    Red Hat Product Security ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2021-18340↗Red Hat Product Security security advisory↗Patch or update reference↗CVE authority or vendor 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-2021-31440 · cve.blacktree.nl