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Out-of-bounds WriteWeakness · CWE-787

CVE-2025-0677

MEDIUM · 6.4 CVSS v3.1 Published 2025-02-19
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
66/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A flaw was found in grub2. When performing a symlink lookup, the grub's UFS module checks the inode's data size to allocate the internal buffer to read the file content, however, it fails to check if the symlink data size has overflown. When this occurs, grub_malloc() may be called with a smaller value than needed. When further reading the data from the disk into the buffer, the grub_ufs_lookup_symlink() function will write past the end of the allocated size. An attack can leverage this by crafting a malicious filesystem, and as a result, it will corrupt data stored in the heap, allowing for arbitrary code execution used to by-pass secure boot mechanisms.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The GRUB2 UFS module fails to validate symlink data size during lookup, causing heap buffer overflow when grub_malloc() allocates insufficient memory based on an overflowing inode size. The grub_ufs_lookup_symlink() function then writes past the allocated buffer bounds, leading to heap corruption that can be exploited via a malicious filesystem to achieve arbitrary code execution and bypass Secure Boot.

MitigationApply the upstream GRUB2 patch to add proper symlink size overflow validation in the UFS module, rebuild and re-sign GRUB2 binaries for Secure Boot enrollment, and ensure only trusted filesystem images are used during boot.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
High
Privileges
High
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify GRUB2 installation and version
    Run 'grub2-install --version' or 'grub-install --version' to get the installed GRUB2 version. On some systems, check /boot/grub2 or /boot/grub for the GRUB directory.
    Affected if The installed GRUB2 version is older than the patched version for CVE-2025-0677 (version information should be compared against upstream security advisories).
  2. Locate the UFS module
    Check for the existence of the UFS module in the GRUB modules directory: look for 'ufs2.mod' or 'ufs1.mod' in /boot/grub2/x86_64-efi/ or /usr/lib/grub/x86_64-efi/ or the equivalent path for your architecture.
    Affected if The UFS module (ufs2.mod) is present in the GRUB installation and can be loaded during boot.
  3. Check if UFS filesystems are in use
    Examine /etc/fstab and mount outputs for entries using 'ufs' as the filesystem type, or check for UFS disk labels/Partitions on BSD or Solaris systems.
    Affected if The system has UFS filesystems configured or present, which would cause GRUB2 to load and use the vulnerable UFS module during boot.
  4. Verify GRUB can be rebuilt
    Check if the GRUB2 package is available from the distribution vendor and can be reinstalled or rebuilt with 'grub2-mkconfig' or 'grub-mkconfig'.
    Affected if You cannot rebuild or update GRUB2 to obtain the patched version, leaving the vulnerable module in place.

You are affected if GRUB2 with the UFS module is installed and the system uses or can boot from UFS filesystems, and the installed GRUB2 version predates the CVE-2025-0677 fix.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the upstream GRUB2 patch to add proper symlink size overflow validation in the UFS module, rebuild and re-sign GRUB2 binaries for Secure Boot enrollment, and ensure only trusted filesystem images are used during boot.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
24.0 hours of engineering $4,160
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-0677 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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