Secure Boot bypass via unsigned kernel loading
Published Mar 15, 2021 · Updated Aug 3, 2024
Improper signature validation in GNU GRUB before 2.06 allows local users with administrative access to bypass UEFI Secure Boot. When GRUB is booted directly under a certificate trusted in UEFI db, its shim_lock verifier accepts and starts a kernel without validating that kernel's signature. The affected state is limited to upstream builds and distributions using shim_lock, and a tampered kernel then runs while the system reports Secure Boot lockdown.
Summary
What happened
Improper signature validation in GNU GRUB before 2.06 allows local users with administrative access to bypass UEFI Secure Boot. When GRUB is booted directly under a certificate trusted in UEFI db, its shim_lock verifier accepts and starts a kernel without validating that kernel's signature. The affected state is limited to upstream builds and distributions using shim_lock, and a tampered kernel then runs while the system reports Secure Boot lockdown.
The record
- CVE
- CVE-2021-3418
- Published
- Mar 15, 2021
- Updated
- Aug 3, 2024
- Vendor
- The GnuPG Project
- Product
- GNU GRUB
- Classifications
- CWE-281, T1542.003
- Attack vector
- local
- Privileges
- admin
Timeline
How it unfolded
- Mar 15, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=Fixed in 2.06
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo