CVE-2021-20027
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 buffer overflow vulnerability in SonicOS allows a remote attacker to cause a Denial of Service (DoS) by sending a specially crafted request. This vulnerability affects SonicOS Gen5, Gen6, Gen7 platforms, and SonicOSv virtual firewalls.
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 confidenceBuffer overflow vulnerability in SonicOS firewall operating system allows remote attackers to cause denial of service via specially crafted requests. The flaw affects Gen5, Gen6, Gen7 platforms and SonicOSv virtual firewalls.
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<= 7.0.1-r1262<= 7.0.1-r.1219<= 7.0.1-r514<= 5.9.1.13<= 6.5.1.12<= 6.5.4.7all versions<= 6.0.5.3-94oCVSS 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
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/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.
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Identify SonicOS version via CLILog into the firewall CLI and run 'show version' or 'get system status' to display the installed firmware version and build numberAffected if The displayed version matches any of the affected ranges: <= 7.0.1-r1262, <= 7.0.1-r1219, <= 7.0.1-r514, <= 5.9.1.13, <= 6.5.1.12, <= 6.5.4.7, <= 6.0.5.3-94o, or is an unpatched version of 'all versions' for the listed platforms
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Verify hardware platform generationFrom the CLI output or web interface (System > Status), identify whether the device is Gen5, Gen6, Gen7, or SonicOSv virtual firewallAffected if The platform is identified as Gen5, Gen6, Gen7, or SonicOSv and the version from step 1 is within the affected ranges
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Check management interface accessibilityFrom an external perspective, verify if the SonicWall management web interface (typically ports 443, 8443) or SSH is reachable from untrusted networksAffected if The management interface is exposed to the internet or untrusted LAN segments without proper access controls, as this is the attack vector for the buffer overflow
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Confirm SNMP monitoring versionIf SNMP is configured, verify which SNMP version is in use and whether the system is responding to SNMP queries that expose version detailsAffected if SNMP exposes system information to unauthorized observers allowing them to confirm the vulnerable version
You are affected if your Sonicwall device runs Gen5, Gen6, Gen7, or SonicOSv with a firmware version matching any of the affected build numbers and the management interface is network-accessible to potential attackers.
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 dataApply vendor-provided patches from SonicWall for all affected SonicOS versions; if patches unavailable, implement network segmentation to restrict access to management interfaces and consider rate limiting as a temporary mitigation.
- Consultation3.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20027 — 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-2021-20027 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
- No weaponised exploit code, or anything meant to cause harm
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