CVE-2021-20106
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 · uneditedNessus Agent versions 8.2.5 and earlier were found to contain a privilege escalation vulnerability which could allow a Nessus administrator user to upload a specially crafted file that could lead to gaining administrator privileges on the Nessus host.
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 confidenceNessus Agent versions 8.2.5 and earlier contain a privilege escalation vulnerability where an authenticated Nessus administrator can upload a specially crafted file that enables the attacker to gain full administrator privileges on the Nessus host system.
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<= 8.2.5CVSS 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
- High
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:H/UI:R/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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Verify Nessus Agent is installedCheck for the Nessus service on Windows (services.msc) or the nessusd process on Linux (ps aux | grep nessusd), or look for the installation directory (Windows: C:\Program Files\Tenable\Nessus, Linux: /opt/nessus)Affected if Nessus Agent is found running or installed on the system
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Determine installed Nessus Agent versionRun 'nessuscli --version' on Linux, check Windows registry at HKLM\SOFTWARE\Tenable\Nessus\InstallPath, or use the Nessus web interface (Help > About)Affected if Unable to determine version or version cannot be verified
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Compare version against affected rangeCheck if the installed version is 8.2.5 or earlier. On Linux, the version may be displayed as 8.2.5 (build X). On Windows, check the file version of nessus-service.exe in the installation directoryAffected if Installed version is 8.2.5 or any version number lower than 8.2.5
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Review Nessus administrative accountsAccess Nessus web interface (typically port 8834) and navigate to Users > Users or check local authentication settings to see which accounts have administrator privilegesAffected if There are one or more Nessus administrator accounts configured (these accounts are required for the attack vector to be exploitable)
A system is affected if Nessus Agent version 8.2.5 or earlier is installed AND there are Nessus administrator accounts present that could be compromised to perform the privilege escalation.
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 dataUpgrade Nessus Agent to a version newer than 8.2.5. Limit administrative access to trusted personnel and monitor for unauthorized privilege escalation attempts.
- Consultation2.0 h
- Implementation2.0 h
- Testing1.0 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 $1,744.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20106 — 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-2021-20106 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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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