CVE-2023-6397
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 · uneditedA null pointer dereference vulnerability in Zyxel ATP series firmware versions from 4.32 through 5.37 Patch 1 and USG FLEX series firmware versions from 4.50 through 5.37 Patch 1 could allow a LAN-based attacker to cause denial-of-service (DoS) conditions by downloading a crafted RAR compressed file onto a LAN-side host if the firewall has the “Anti-Malware” feature enabled.
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 Zyxel ATP (firmware 4.32 through 5.37 Patch 1) and USG FLEX (firmware 4.50 through 5.37 Patch 1) firewalls when the Anti-Malware feature is enabled. A LAN-based attacker can cause denial-of-service by triggering the anti-malware scanning engine with a crafted RAR compressed file, leading to a crash of the scanning service.
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>= 4.32, < 5.37= 5.37>= 4.32, < 5.37= 5.37>= 4.32, < 5.37= 5.37>= 4.32, < 5.37= 5.37>= 4.32, < 5.37= 5.37>= 4.32, < 5.37= 5.37>= 4.50, < 5.37= 5.37>= 4.50, < 5.37= 5.37CVSS 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
- Adjacent
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:A/AC:H/PR:N/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.
-
Identify the Zyxel device modelAccess the device web UI or CLI and retrieve the model name (e.g., ATP100, ATP200, USG Flex 100, etc.) from the status or system information page.Affected if The device is not an ATP or USG FLEX series model.
-
Check the installed firmware versionNavigate to the device web UI System > Firmware or use the CLI command 'show system-info' to retrieve the current firmware version.Affected if The firmware version is 4.32 through 5.37 Patch 1 (inclusive) for ATP devices, or 4.50 through 5.37 Patch 1 for USG FLEX devices.
-
Verify the Anti-Malware feature statusIn the device web UI, go to Security > Anti-Malware (or Anti-Virus) and check whether the feature is enabled or disabled. Alternatively, use the CLI command 'show anti-malware status' if available.Affected if The Anti-Malware feature is currently enabled on the device.
A device is affected if it is a Zyxel ATP or USG FLEX firewall running firmware 4.32 to 5.37 Patch 1 (or 4.50+ for USG FLEX) AND the Anti-Malware feature is enabled, allowing a LAN attacker to crash the scanning service with a crafted RAR file.
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 data5.37
Disable the Anti-Malware feature on affected devices until the firmware can be updated to a patched version, or apply the vendor firmware update (5.37 Patch 2 or later) to remediate the vulnerability.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-6397 — 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-2023-6397 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data