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Full vulnerability report · 2021
CVE-2021-3490High confidence

Linux kernel eBPF bitwise ops ALU32 bounds tracking

Linux · Linux kernel

7.8HighCVSS 3.1
Recommended action
Within 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
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-2021-3490 · CSAF 2.0 · revision 3 · status not statedRed Hat Product Securitykernel: Linux kernel eBPF bitwise ops ALU32 bounds tracking
101 known not affected

The vendor explicitly states that these products are not affected by this CVE.

  • kernel as a component of Red Hat Enterprise Linux 6
  • kernel-abi-whitelists as a component of Red Hat Enterprise Linux 6
  • kernel-bootwrapper as a component of Red Hat Enterprise Linux 6
  • kernel-debug as a component of Red Hat Enterprise Linux 6
  • kernel-debug-devel as a component of Red Hat Enterprise Linux 6
  • kernel-devel as a component of Red Hat Enterprise Linux 6
  • kernel-doc as a component of Red Hat Enterprise Linux 6
  • kernel-firmware as a component of Red Hat Enterprise Linux 6
  • kernel-headers as a component of Red Hat Enterprise Linux 6
  • kernel-kdump as a component of Red Hat Enterprise Linux 6
  • kernel-kdump-devel as a component of Red Hat Enterprise Linux 6
  • kernel.src as a component of Red Hat Enterprise Linux 6
Summary
A flaw was found in the Linux kernels eBPF verification code. It was discovered that eBPF ALU32 bounds tracking for bitwise ops (AND, OR and XOR) did not update the 32-bit bounds. By default accessing the eBPF verifier is only accessible to privileged users with CAP_SYS_ADMIN. A local user with the ability to insert eBPF instructions could use this flaw to crash the system or possibly escalate their privileges on the system.
Remediation
No remediation text is recorded.
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-2021-26812

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 with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

The eBPF ALU32 bounds tracking for bitwise ops (AND, OR and XOR) in the Linux kernel did not properly update 32-bit bounds, which could be turned into out of bounds reads and writes in the Linux kernel and therefore, arbitrary code execution. This issue was fixed via commit 049c4e13714e ("bpf: Fix alu32 const subreg bound tracking on bitwise operations") (v5.13-rc4) and backported to the stable kernels in v5.12.4, v5.11.21, and v5.10.37. The AND/OR issues were introduced by commit 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking") (5.7-rc1) and the XOR variant was introduced by 2921c90d4718 ("bpf:Fix a verifier failure with xor") ( 5.10-rc1).

What

The eBPF ALU32 bounds tracking for bitwise ops (AND, OR and XOR) in the Linux kernel did not properly update 32-bit bounds, which could be turned into out of bounds reads and writes in the Linux kernel and therefore, arbitrary code execution. This issue was fixed via commit 049c4e13714e ("bpf: Fix alu32 const subreg bound tracking on bitwise operations") (v5.13-rc4) and backported to the stable kernels in v5.12.4, v5.11.21, and v5.10.37. The AND/OR issues were introduced by commit 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking") (5.7-rc1) and the XOR variant was introduced by 2921c90d4718 ("bpf:Fix a verifier failure with xor") ( 5.10-rc1).

Why

A bounds error lets data be written beyond the intended memory region, potentially corrupting control data.

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

The eBPF ALU32 bounds tracking for bitwise ops (AND, OR and XOR) in the Linux kernel did not properly update 32-bit bounds, which could be turned into out of bounds reads and writes in the Linux kernel and therefore, arbitrary code execution. This issue was fixed via commit 049c4e13714e ("bpf: Fix alu32 const subreg bound tracking on bitwise operations") (v5.13-rc4) and backported to the stable kernels in v5.12.4, v5.11.21, and v5.10.37. The AND/OR issues were introduced by commit 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking") (5.7-rc1) and the XOR variant was introduced by 2921c90d4718 ("bpf:Fix a verifier failure with xor") ( 5.10-rc1).

Why

A bounds error lets data be written beyond the intended memory region, potentially corrupting control data.

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.
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 → Out-of-bounds Write → 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
Changed: exploitation can affect a different security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-787 ↗

CWE-787: Out-of-bounds Write. The product writes data past the end, or before the beginning, of the intended buffer.

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:C/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.SChangedScope: The attack can affect a component governed by a different security 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-787Public 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-20210609Security Bulletin 09 Jun 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 09 Jun 2021, published on 9 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-751Multiples vulnérabilités dans Google Android

ord?id=CVE-2021-30292 Référence CVE CVE-2021-30297 https://www.cve.org/CVERecord?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-500Multiples vulnérabilités dans le noyau Linux de SUSE

ecord?id=CVE-2020-36386 Référence CVE CVE-2021-0129 https://www.cve.org/CVERecord?id=CVE-2021-0129 Référence CVE CVE-2021-23134 https://www.cve.org/CVERecord?id=CVE-2021-23134 Référence CVE CVE-2021-28660 https://www.cve.org/CVERecord?id=CVE-2021-28660 Référence CVE CVE-2021-29154 https://www.cve.org/CVERecord?id=CVE-2021-29154 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-2021-3489 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-2021-3491 https://www.cve.org/CVERecord?id=CVE-2021-3491 Gestion détaillée du document le 01 juillet 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-469Multiples vulnérabilités dans le noyau Linux de SUSE

CVERecord?id=CVE-2021-29650 Référence CVE CVE-2021-30002 https://www.cve.org/CVERecord?id=CVE-2021-30002 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-2021-3428 https://www.cve.org/CVERecord?id=CVE-2021-3428 Référence CVE CVE-2021-3444 https://www.cve.org/CVERecord?id=CVE-2021-3444 Référence CVE CVE-2021-3483 https://www.cve.org/CVERecord?id=CVE-2021-3483 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-2021-3491 https://www.cve.org/CVERecord?id=CVE-2021-3491 Gestion détaillée du document le 17 juin 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-372Multiples vulnérabilités dans le noyau Linux d'Ubuntu

ecord?id=CVE-2021-29646 Référence CVE CVE-2021-29647 https://www.cve.org/CVERecord?id=CVE-2021-29647 Référence CVE CVE-2021-29649 https://www.cve.org/CVERecord?id=CVE-2021-29649 Référence CVE CVE-2021-29650 https://www.cve.org/CVERecord?id=CVE-2021-29650 Référence CVE CVE-2021-29657 https://www.cve.org/CVERecord?id=CVE-2021-29657 Référence CVE CVE-2021-30002 https://www.cve.org/CVERecord?id=CVE-2021-30002 Référence CVE CVE-2021-31916 https://www.cve.org/CVERecord?id=CVE-2021-31916 Référence CVE CVE-2021-3483 https://www.cve.org/CVERecord?id=CVE-2021-3483 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-2021-3491 https://www.cve.org/CVERecord?id=CVE-2021-3491 Référence CVE CVE-2021-3493 https://www.cve.org/CVERecord?id=CVE-2021-3493 Gestion détaillée du document le 14 mai 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 ↗
JVN iPedia · Japanese · JVNDB-2021-012328Linux Kernel における境界外読み取りに関する脆弱性

Linux Kernel には、境界外読み取りに関する脆弱性、および境界外書き込み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.
Patch available
Affected
Linux kernel: trunk < v5.13-rc4, linux-5.12.y < v5.12.4, linux-5.11.y < v5.11.21, linux-5.10.y < v5.10.37, v5.7-rc1 < 5.7*
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
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 4 Jun 2021 · Last source change 16 Sept 2024, 22:29 UTC · CWE-787 · Out-of-bounds Write

CVE recordCVE.org · 5.1
CVSS sourceCNA
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-2021-26812
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
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2021-26812↗Vendor CSAF · Red Hat Product Security↗Patch or update reference↗Patch or update reference↗CVE authority or vendor reference↗Public exploit 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-2021-3490 · cve.blacktree.nl