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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 5 Apr 2022.
SonicosOperating system · Sonicwall

CVE-2020-5135

CRITICAL · 9.8 CVSS v3.1 Published 2020-10-12
Fix available
A fix is available. Upgrade to after 6.5.4.7 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild Remotely reachable No privileges Zero-click

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 · unedited
A buffer overflow vulnerability in SonicOS allows a remote attacker to cause Denial of Service (DoS) and potentially execute arbitrary code by sending a malicious request to the firewall. This vulnerability affected SonicOS Gen 6 version 6.5.4.7, 6.5.1.12, 6.0.5.3, SonicOSv 6.5.4.v and Gen 7 version 7.0.0.0.

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 confidence

Buffer overflow vulnerability in SonicOS firewall allows remote attackers to send malicious requests causing denial of service and potentially execute arbitrary code. The flaw affects specific versions of SonicOS Gen 6, SonicOSv, and Gen 7.

MitigationApply vendor-supplied patches for affected versions (SonicOS Gen 6: 6.5.4.7, 6.5.1.12, 6.0.5.3; SonicOSv 6.5.4.v; Gen 7: 7.0.0.0) or upgrade to patched releases. Implement network-level filtering as interim control.

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
SonicosOperating system
Affected:<= 6.0.5.3>= 6.5.0.0, <= 6.5.1.11>= 6.5.4.0, <= 6.5.4.7= 7.0.0.0
SonicosvOperating system
Affected:<= 6.5.4.4

CVSS 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
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify product family
    Confirm the device runs SonicOS (physical firewall) or SonicOSv (virtual appliance) as the operating system
    Affected if Product is not SonicOS or SonicOSv - not affected
  2. Locate version information
    Access the firewall web UI dashboard, CLI show command, or system status page to obtain the current SonicOS firmware version number
    Affected if Cannot determine version - further investigation needed
  3. Compare version to affected ranges
    Match the installed version against the vulnerable ranges: SonicOS <= 6.0.5.3, 6.5.0.0-6.5.1.11, 6.5.4.0-6.5.4.7, or exactly 7.0.0.0; SonicOSv <= 6.5.4.4
    Affected if Installed version falls within any of these ranges - affected by CVE-2020-5135

If the installed SonicOS or SonicOSv version matches any of the specified vulnerable ranges, the environment is affected by this buffer overflow vulnerability.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Upgrade available Upgrade to a release after 6.5.4.7
Interim mitigation

Apply vendor-supplied patches for affected versions (SonicOS Gen 6: 6.5.4.7, 6.5.1.12, 6.0.5.3; SonicOSv 6.5.4.v; Gen 7: 7.0.0.0) or upgrade to patched releases. Implement network-level filtering as interim control.

Recommended fix Moderate confidence

Sonicos 6.0.5.4+, 6.5.1.13+, 6.5.4.8+, 7.0.0.1+; Sonicosv 6.5.4.5+

  1. 1. Identify the exact SonicOS or SonicOSv version currently running on the firewall device
  2. 2. Based on the identified version, upgrade to the first fixed release in that release line: For Sonicos 6.0.x, upgrade to 6.0.5.4 or later; For Sonicos 6.5.1.x, upgrade to 6.5.1.13 or later; For Sonicos 6.5.4.x, upgrade to 6.5.4.8 or later; For Sonicos 7.0.x, upgrade to 7.0.0.1 or later; For Sonicosv 6.5.4.x, upgrade to 6.5.4.5 or later
  3. 3. Obtain the firmware from the official SonicWall download portal at https://www.sonicwall.com/support/ or through the MySonicWall customer portal
  4. 4. Review SonicWall release notes to confirm the specific version includes the CVE-2020-5135 fix
  5. 5. Upload and apply the firmware upgrade through the firewall management interface or via CLI
  6. 6. After upgrade, verify the new firmware version is running and test firewall functionality
Caveat Review release notes for migration path between major versions; firmware upgrade may cause brief service interruption

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Sonicos Exploited in the wild — priority engagement
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-5135 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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