FreeBSDOperating system
CVE-2020-10566
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 · uneditedgrub2-bhyve, as used in FreeBSD bhyve before revision 525916 2020-02-12, mishandles font loading by a guest through a grub2.cfg file, leading to a buffer overflow.
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 · moderate confidenceA buffer overflow vulnerability exists in grub2-bhyve, the GRUB2 bootloader used by FreeBSD's bhyve hypervisor. The flaw occurs in the font loading mechanism when a guest VM provides a specially crafted grub2.cfg file. The font loading routine fails to properly validate buffer boundaries before copying font data, allowing a guest to overflow the allocated buffer and potentially execute code in the hypervisor context.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
FreeBSDOperating system
< 525916_2020-02-12CVSS 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
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/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 checksWork through these to decide whether this CVE applies to you.
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Confirm FreeBSD is the host operating systemRun 'uname -a' or 'freebsd-version' to verify the host is running FreeBSDAffected if The host is running FreeBSD with bhyve installed
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Identify bhyve/grub2-bhyve revisionCheck the bhyve or grub2-bhyve package revision. On FreeBSD, examine the installed package version or check the source revision if built from ports. Look for the revision number 525916 or date 2020-02-12 as reference points.Affected if The installed bhyve/grub2-bhyve revision is earlier than 525916 or was built before 2020-02-12
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Verify guest VM configuration accessReview file permissions on the directory containing guest grub2.cfg files. Check if untrusted users can write to or supply these configuration files.Affected if Untrusted users or guest VMs can provide or modify grub2.cfg files without review
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Check for custom or untrusted guest configurationsAudit all guest VM configurations to identify any that load grub2.cfg files from untrusted or externally controlled sourcesAffected if Guest VMs use grub2.cfg files from untrusted or attacker-controlled sources
A system is affected if it runs FreeBSD with bhyve/grub2-bhyve versions prior to revision 525916 (pre-2020-02-12) and permits untrusted guest VMs to provide grub2.cfg files to the font loading mechanism.
Generated from the published advisory. Verify against your own configuration.
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 data525916_2020-02-12
Update bhyve to revision 525916 or later (2020-02-12 onwards). Until the patch is applied, ensure that guest grub2.cfg files are from trusted sources only and do not allow untrusted users to control hypervisor configuration.
Fix this in FreeBSD
Scoped from the published advisory
- Consultation3.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,224.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-10566 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-10566 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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