How to check if you are exposed to CVE-2021-42287
- Find every Microsoft Active Directory system you or your clients run, including ones exposed to the internet. Those come first: CISA only lists flaws attackers are already using.
- Compare each version with the fixed versions in the vendor advisory. Where no fix exists yet, apply the vendor’s mitigation or take the system off the internet.
- Run a credentialed vulnerability scan to catch the systems you missed, then check that the next scan no longer reports CVE-2021-42287.
US federal agencies had to fix this by 2022-05-02. Everyone else should treat that deadline as a guide: if it has passed, this is overdue.
Affected versions
Versions the National Vulnerability Database lists as vulnerable to CVE-2021-42287. Check the vendor advisory for the exact fixed builds before you sign anything off.
| Product | Vulnerable versions |
|---|---|
| Microsoft Windows Server 2004 | before 10.0.19041.1348 |
| Microsoft Windows Server 2008 | --sp2; r2-sp1 |
| Microsoft Windows Server 2012 | all versions; r2 |
| Microsoft Windows Server 2016 | before 10.0.14393.4770 |
| Microsoft Windows Server 2019 | before 10.0.17763.2300 |
| Microsoft Windows Server 2022 | before 10.0.20348.350 |
NVD lists 1 more affected product; see the full record on NVD.
Timeline
- · Published in the National Vulnerability Database
- · Added to CISA's Known Exploited Vulnerabilities catalog, 152 days after it was published
- · Fix-by date for US federal agencies, passed 1,644 days ago
Weakness type
More exploited Microsoft vulnerabilities
CISA lists 390 exploited Microsoft vulnerabilities. The closest matches:
- CVE-2022-26923Microsoft Active Directory Domain Services Privilege Escalation VulnerabilityAdded 2022-08-18
- CVE-2021-42278Microsoft Active Directory Domain Services Privilege Escalation VulnerabilityAdded 2022-04-11
- CVE-2026-96951Microsoft Windows Command Injection VulnerabilityAdded 2026-10-13
- CVE-2026-65660Microsoft SharePoint Code Injection VulnerabilityAdded 2026-09-25
- CVE-2026-85880Microsoft Windows Heap-Based Buffer Overflow VulnerabilityAdded 2026-09-08
- CVE-2026-81963Microsoft Windows Link Following VulnerabilityAdded 2026-09-08
- CVE-2019-1068Microsoft SQL Server Remote Code Execution VulnerabilityAdded 2026-08-26
- CVE-2026-55040Microsoft SharePoint Weak Authentication VulnerabilityAdded 2026-08-18
Keep going
Sources: CISA Known Exploited Vulnerabilities catalog (version 2026.10.30); EPSS data from FIRST.org; CVSS and descriptions from the NIST National Vulnerability Database. Checked 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.