CVE-2021-20100
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 8.2.4 and earlier for Windows were found to contain multiple local privilege escalation vulnerabilities which could allow an authenticated, local administrator to run specific Windows executables as the Nessus host. This is different than CVE-2021-20099.
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 confidenceNessus Agent 8.2.4 and earlier for Windows contains multiple local privilege escalation vulnerabilities. An authenticated local administrator can exploit these to run specific Windows executables with the privileges of the Nessus service account, effectively elevating their privileges beyond their current administrative rights.
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
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:H/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 checksWork through these to decide whether this CVE applies to you.
-
Check if Nessus Agent is installedOpen Windows Registry Editor and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Tenable\Nessus\Installed or check C:\Program Files\Tenable\Nessus for the installation directoryAffected if Nessus Agent is installed on the system
-
Determine the installed Nessus Agent versionCheck the Version value in HKEY_LOCAL_MACHINE\SOFTWARE\Tenable\Nessus\Installed, or run 'nessuscli --version' from the Nessus installation directoryAffected if The installed version is 8.2.4 or earlier (versions prior to 8.2.5)
-
Verify current user privilegesRun 'whoami /groups' or check if the current user is a member of the Administrators group on the systemAffected if The current user has local administrator privileges
-
Check if Nessus service is runningOpen Services console (services.msc) and locate the 'Nessus Agent' service, or run 'sc query nessus' from command promptAffected if The Nessus Agent service is installed and running on the system
A user is affected if Nessus Agent version 8.2.4 or earlier is installed on Windows and the current user has local administrator privileges, allowing potential privilege escalation via the vulnerable executables.
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 data8.2.5
Update Nessus Agent to a version newer than 8.2.4. Additionally, restrict local administrator access and apply least-privilege principles to limit the attack surface.
- Consultation2.0 h
- Implementation2.0 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 $1,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20100 — 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-2021-20100 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