CVE-2021-3418 Security feature bypass in grub2
Attackers can bypass Secure Boot signature validation to boot tampered kernels, enabling privilege escalation and code execution on affected systems.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-3418?
CVE-2021-3418 is a medium-severity vulnerability in grub2, published on 15 Mar 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
If certificates that signed grub are installed into db, grub can be booted directly. It will then boot any kernel without signature validation. The booted kernel will think it was booted in secureboot mode and will implement lockdown, yet it could have been tampered. This flaw is a reintroduction of CVE-2020-15705 and only affects grub2 versions prior to 2.06 and upstream and distributions using the shim_lock mechanism.
Weakness: CWE-281
Which versions are affected by CVE-2021-3418?
It affects 1 product.
Products include Gnu Grub2.
How do I fix CVE-2021-3418?
Upgrade to a fixed version.
Is CVE-2021-3418 being exploited?
There is no known exploitation of CVE-2021-3418 in the wild and no public exploit code.
Other vulnerabilities in grub2
- CVE-2024-56737 Memory corruption in GRUB2
- CVE-2022-28733 Integer underflow in grub_net_recv_ip4_packets
- CVE-2022-28734 Out-of-bounds write when handling split HTTP headers
- CVE-2025-61662 Grub2: missing unregister call for gettext command may lead to use-after-free
- CVE-2024-45782 Grub2: fs/hfs: strcpy() using the volume name (fs/hfs.c:382)
Sources
Also known as ALPINE-CVE-2021-3418, AZL-6467, GHSA-j6wm-c7q8-jcx7.