FreeBSDOperating system
CVE-2020-24385
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 · uneditedIn MidnightBSD before 1.2.6 and 1.3 before August 2020, and FreeBSD before 7, a NULL pointer dereference was found in the Linux emulation layer that allows attackers to crash the running kernel. During binary interaction, td->td_emuldata in sys/compat/linux/linux_emul.h is not getting initialized and returns NULL from em_find().
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 confidenceA NULL pointer dereference vulnerability exists in the Linux emulation layer of MidnightBSD and FreeBSD where the td->td_emuldata field in sys/compat/linux/linux_emul.h is not properly initialized, causing em_find() to return NULL during binary interaction and leading to kernel crashes.
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
<= 7.0< 1.2.6>= 1.3, <= 2020-08-19CVSS 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
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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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Identify the operating system and versionRun `uname -a` or check /etc/os-release to determine if the system is FreeBSD or MidnightBSD and note the exact version numberAffected if The version is FreeBSD <= 7.0 OR MidnightBSD < 1.2.6 OR (MidnightBSD >= 1.3 AND the build date is on or before 2020-08-19)
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Determine if Linux emulation is enabledCheck if the Linux binary compatibility module is loaded by running `kldstat` or checking for linux.ko, or look for `linux_enable="YES"` in /etc/rc.confAffected if Linux emulation layer is loaded or enabled on a vulnerable version of the OS
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Verify the kernel source for proper initializationIf kernel source is available, examine sys/compat/linux/linux_emul.h and look for the initialization of td->td_emuldata field in the thread structure, specifically before calls to em_find()Affected if The td_emuldata field is not properly initialized in the Linux emulation layer code
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Check for kernel crashes related to Linux binariesReview system logs (dmesg, /var/log/messages) for kernel panics or crashes mentioning NULL pointer dereference in linux_emul or em_find functions when running Linux binariesAffected if Kernel crashes occur when executing Linux binaries on an affected system with Linux emulation enabled
A system is affected if it runs a vulnerable version of FreeBSD <= 7.0 or MidnightBSD (< 1.2.6 or >= 1.3 through 2020-08-19) with the Linux emulation layer enabled, and exhibits kernel crashes when running Linux binaries.
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 data1.2.6
Apply vendor security updates for MidnightBSD 1.2.6+/1.3+ (August 2020) or FreeBSD 7+ to properly initialize td_emuldata in the Linux emulation layer, or disable Linux emulation if not required.
Fix this in FreeBSD
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-24385 — 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-2020-24385 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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