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Full vulnerability report · 2020
CVE-2020-15705High confidence

GRUB2: avoid loading unsigned kernels when GRUB is booted directly under secureboot without shim

Ubuntu · grub2 in Ubuntu

6.4MediumCVSS 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.

Patch available
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-2020-7691

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.

Patch available
01

What, why and how

GRUB2 fails to validate kernel signature when booted directly without shim, allowing secure boot to be bypassed. This only affects systems where the kernel signing certificate has been imported directly into the secure boot database and the GRUB image is booted directly without the use of shim. This issue affects GRUB2 version 2.04 and prior versions.

What

GRUB2 fails to validate kernel signature when booted directly without shim, allowing secure boot to be bypassed. This only affects systems where the kernel signing certificate has been imported directly into the secure boot database and the GRUB image is booted directly without the use of shim. This issue affects GRUB2 version 2.04 and prior versions.

Why

The product does not verify, or incorrectly verifies, the cryptographic signature for data.

How

An attacker operating through local access may attempt exploitation with elevated privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

GRUB2 fails to validate kernel signature when booted directly without shim, allowing secure boot to be bypassed. This only affects systems where the kernel signing certificate has been imported directly into the secure boot database and the GRUB image is booted directly without the use of shim. This issue affects GRUB2 version 2.04 and prior versions.

Why

The product does not verify, or incorrectly verifies, the cryptographic signature for data.

How

An attacker operating through local access may attempt exploitation with elevated 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 → Improper Verification of Cryptographic Signature → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Local
Privileges required
High: elevated access 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-347 ↗

CWE-347: Improper Verification of Cryptographic Signature. The product does not verify, or incorrectly verifies, the cryptographic signature for data.

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:H/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.PRHighPrivileges required: The attacker needs elevated or administrative 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-347
A

Official authority intelligence

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

BSI · German · WID-SEC-W-2022-0553Grub2: Mehrere Schwachstellen ermöglichen Umgehen von Sicherheitsvorkehrungen

Ein lokaler Angreifer mit Administratorrechten oder physischem Zugriff auf das Gerät, kann mehrere Schwachstellen in Grub2 ausnutzen, um Sicherheitsvorkehrungen zu umgehen.

Official advisory
CERT-FR · French · CERTFR-2022-AVI-267Multiples vulnérabilités dans Juniper Networks Junos Space

d?id=CVE-2020-14308 Référence CVE CVE-2020-14309 https://www.cve.org/CVERecord?id=CVE-2020-14309 Référence CVE CVE-2020-14310 https://www.cve.org/CVERecord?id=CVE-2020-14310 Référence CVE CVE-2020-14311 https://www.cve.org/CVERecord?id=CVE-2020-14311 Référence CVE CVE-2020-14314 https://www.cve.org/CVERecord?id=CVE-2020-14314 Référence CVE CVE-2020-14331 https://www.cve.org/CVERecord?id=CVE-2020-14331 Référence CVE CVE-2020-14363 https://www.cve.org/CVERecord?id=CVE-2020-14363 Référence CVE CVE-2020-14364 https://www.cve.org/CVERecord?id=CVE-2020-14364 Référence CVE CVE-2020-14385 https://www.cve.org/CVERecord?id=CVE-2020-14385 Référence CVE CVE-2020-15705 https://www.cve.org/CVERecord?id=CVE-2020-15705 Référence CVE CVE-2020-15706 https://www.cve.org/CVERecord?id=CVE-2020-15706 Référence CVE CVE-2020-15707 https://www.cve.org/CVERecord?id=CVE-2020-15707 Référence CVE CVE-2020-15999 https://www.cve.org/CVERecord?id=CVE-2020-15999 Référence CVE CVE-2020-1749 https://www.cve.org/CVERecord?id=CVE-2020-1749 Référence CVE CVE-2020-1983 https://www.cve.org/CVERecord?id=CVE-2020-1983 Référence CVE CVE-2020-24394 https://www.cve.org/CVERecord?id=CVE-2020-24394 Référence CVE CVE-2020-25212 https://www.cve.org/CVERecord?id=CVE-2020-25212 Référence CVE CVE-2020-25637 https://www.cve.org/CVERecord?id=CVE-

Official advisory
CERT-FR · French · CERTFR-2021-AVI-172Multiples vulnérabilités dans GRUB

GRUB2 est le bootloader le plus couramment utilisé par les distributions Linux pour démarrer le système d'exploitation. De multiples vulnérabilités ont été découvertes dans GRUB2. Elles permettent à un attaquant, ayant la possibilité de passer une commande à GRUB2 ou de manipuler d'autres ressources utilisées par GRUB2, de provoquer une exécution de code arbitraire. Pour y parvenir, l'attaquant doit avoir les droits administrateurs ou avoir un accès physique à un équipement afin de manipuler la séquence de démarrage (via un support amovible ou via la modification du disque de boot de la machine). Ces méthodes permettent donc de compromettre une machine même si celle-ci n'a pas Linux d'installé à l'origine. En agissant ainsi sur une machine configurée avec Secure Boot, l'attaquant est alors en capacité de rompre la chaîne de confiance et de déployer du code malveillant pour compromettre la machine de façon persistante sans être détecté.

Official advisory
CERT-FR · French · CERTFR-2020-AVI-485Multiples vulnérabilités dans le noyau Linux d'Ubuntu

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

Official advisory
CERT-FR · French · CERTFR-2020-AVI-476Multiples vulnérabilités dans le noyau Linux d'Ubuntu

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

Official advisory
CERT-FR · French · CERTFR-2020-AVI-477Multiples vulnérabilités dans Grub2

GRUB2 est le bootloader le plus couramment utilisé par les distributions Linux pour démarrer le système d'exploitation. De multiples vulnérabilités ont été découvertes dans GRUB2. Elles permettent à un attaquant, ayant la possibilité de modifier le fichier de configuration grub.cfg ou de manipuler d'autres ressources utilisées par GRUB2, de provoquer une exécution de code arbitraire. Pour y parvenir, l'attaquant doit avoir les droits administrateurs ou avoir un accès physique à un équipement afin de manipuler la séquence de démarrage (via un support amovible ou via la modification du disque de boot de la machine). Ces méthodes permettent donc de compromettre une machine même si celle-ci n'a pas Linux d'installé à l'origine. En agissant ainsi sur une machine configurée avec Secure Boot, l'attaquant est alors en capacité de rompre la chaîne de confiance et de déployer du code malveillant pour compromettre la machine de façon persistante sans être détecté.

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
20.04 LTS < 2.04-1ubuntu26.1; 18.04 LTS < 2.02-2ubuntu8.16; 16.04 LTS < 2.02~beta2-36ubuntu3.26; 14.04 ESM < 2.02~beta2-9ubuntu1.20
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 29 Jul 2020 · Last source change 17 Sept 2024, 00:06 UTC · CWE-347 · Improper Verification of Cryptographic Signature

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-2020-7691
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-2020-7691↗Patch or update reference↗Vendor advisory↗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-2020-15705 · cve.blacktree.nl