Security readout for executives and security teams
Plain-English summary
This issue affects Nessus Agent for Windows version 8.2.4 and earlier. A person who is already authenticated as a local administrator may be able to run certain Windows executables under the Nessus host context, increasing control over that system.
Executive priority
Treat this as a targeted remediation item for Windows systems running Nessus Agent. It is not documented as remotely exploitable or actively exploited in the provided sources, but privileged security tooling should be kept current.
Technical view
CVE-2021-20099 describes multiple local privilege escalation flaws in Nessus Agent 8.2.4 and earlier on Windows. The source states authenticated local administrators can run specific Windows executables as the Nessus host. It is distinct from CVE-2021-20100.
Likely exposure
Exposure is limited to Windows systems running Nessus Agent 8.2.4 or earlier. The described prerequisite is authenticated local administrator access, so broad remote exposure is not supported by the provided sources.
Exploitation context
The provided bundle does not show CISA KEV listing or any cited evidence of active exploitation. The attack context is local and authenticated, with local administrator privileges already required.
Researcher notes
Evidence is sparse in the provided bundle: no CVSS, CWE, detailed root cause, or fixed version is included. Analysis should stay anchored to Tenable’s advisory and asset inventory rather than assuming exploitability beyond the stated local administrator prerequisite.
Mitigation direction
- Inventory Windows hosts running Nessus Agent.
- Identify Nessus Agent versions 8.2.4 or earlier.
- Review Tenable advisory TNS-2021-12 for vendor remediation guidance.
- Upgrade or remediate according to Tenable’s confirmed guidance.
- Restrict and monitor local administrator access on affected hosts.
Validation and detection
- Confirm installed Nessus Agent versions on Windows endpoints.
- Verify whether any affected hosts remain at 8.2.4 or earlier.
- Review endpoint logs for unusual execution under Nessus-related context.
- Confirm local administrator membership is limited and justified.
- Document remediation status for each affected host.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
Privilege behavior lookup
The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-20099 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://www.tenable.com/security/tns-2021-12CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.