CVE-2021-42287
Active Directory Domain Services Elevation of Privilege Vulnerability
- CVSS
- 7.5Highscored by the publisher (CNA)
- Exploited in the wild
- Yes, in CISA KEV since 11 Apr 2022CISA deadline for US federal agencies: 2 May 2022known use in ransomware campaignsunvetted proof-of-concept code on github
- EPSS
- 77.2%chance of exploitation in the next 30 daystop 0.5% of scored CVEsFIRST score of 11 Nov 2026
- Fix
- Patch availablesee the advisories in the references
- Published
- 10 Nov 2021analysed here 12 Nov 2026
Do first. Apply updates per vendor instructions. (CISA's required action for this KEV entry)
Summary
Triage
- Exploitable
- At runtime
- Attack vector
- network
- Can a WAF block it?
- No. See why
The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.
Affected products
| Product | Affected versions | Vendor says fixed in |
|---|---|---|
| Microsoft Windows Server 2008 R2 Service Pack 1 | >= 6.1.7601.0 and < 6.1.7601.25769Vendor says fixed in: not stated | |
| Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) | >= 6.1.7601.0 and < 6.1.7601.25769Vendor says fixed in: not stated | |
| Microsoft Windows Server 2008 Service Pack 2 | >= 6.0.6003.0 and < 6.0.6003.21282Vendor says fixed in: not stated | |
| Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) | >= 6.0.6003.0 and < 6.0.6003.21282Vendor says fixed in: not stated | |
| Microsoft Windows Server 2012 | >= 6.2.9200.0 and < 6.2.9200.23517Vendor says fixed in: not stated | |
| Microsoft Windows Server 2012 R2 | >= 6.3.9600.0 and < 6.3.9600.20174Vendor says fixed in: not stated | |
| Microsoft Windows Server 2012 R2 (Server Core installation) | >= 6.3.9600.0 and < 6.3.9600.20174Vendor says fixed in: not stated | |
| Microsoft Windows Server 2012 (Server Core installation) | >= 6.2.9200.0 and < 6.2.9200.23517Vendor says fixed in: not stated | |
| Microsoft Windows Server 2016 | >= 10.0.14393.0 and < 10.0.14393.4770Vendor says fixed in: not stated | |
| Microsoft Windows Server 2016 (Server Core installation) | >= 10.0.14393.0 and < 10.0.14393.4770Vendor says fixed in: not stated | |
| Microsoft Windows Server 2019 | >= 10.0.17763.0 and < 10.0.17763.2300Vendor says fixed in: not stated | |
| Microsoft Windows Server 2019 (Server Core installation) | >= 10.0.17763.0 and < 10.0.17763.2300Vendor says fixed in: not stated | |
| Microsoft Windows Server 2022 | >= 10.0.20348.0 and < 10.0.20348.350Vendor says fixed in: not stated | |
| Microsoft Windows Server version 2004 | >= 10.0.0 and < 10.0.19041.1348Vendor says fixed in: not stated | |
| Microsoft Windows Server version 20H2 | >= 10.0.0 and < 10.0.19041.1348Vendor says fixed in: not stated |
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
Products named in our analysis
- microsoft:windows_server_2004
- microsoft:windows_server_2008
- microsoft:windows_server_2012
- microsoft:windows_server_2016
- microsoft:windows_server_2019
- microsoft:windows_server_2022
- microsoft:windows_server_20h2
Fix and mitigation
WAF and other mitigations
Can a WAF block it? No. The vulnerability involves elevation of privilege within Active Directory Domain Services, which requires local or authenticated access to the system. It is not triggered by HTTP requests, so a web application firewall cannot filter or block the attack.
Also consider: patch
Based on an AI reading of the CVE description, and no vendor rule found yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Remediation steps (AI-written)
Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.
Exploitation evidence
- CISA KEV catalog
- Listed since 11 Apr 2022. Known use in ransomware campaigns.
- CISA due date
- 2 May 2022, the remediation deadline for US federal agencies
- CISA required action
- Apply updates per vendor instructions.
- Public exploit code
- Unvetted proof-of-concept code on GitHub: 7 GitHub proofs of concept
- CISA SSVC
- exploitation active, automatable no, technical impact totalAssessed by CISA 19 Aug 2025 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.
GitHub proofs of concept
- cube0x0/noPac1,416 stars
- knightswd/NoPacScan87 stars
- ricardojba/Invoke-noPac62 stars
- XiaoliChan/Invoke-sAMSpoofing39 stars
and 3 more repositories
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
Timeline
- 10 Nov 2021Published
- 11 Dec 2021First proof-of-concept repository on GitHub (unvetted)31 days later
- 11 Apr 2022Added to CISA KEV (exploited in the wild)121 days (about 4 months) later
- 2 May 2022CISA remediation due date (US federal agencies)21 days later
- 19 Aug 2025CISA SSVC assessment: exploitation active1,205 days (about 3 years) later
- 19 Aug 2026CVE record last updated366 days (about 1 year) later
- 12 Nov 2026Analysed by vulneraibility.com85 days (about 3 months) later
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
| Metric | Value | What it means |
|---|---|---|
| Attack vector | NetworkReachable over the internet or any routable network. | Reachable over the internet or any routable network. |
| Attack complexity | HighNeeds specific conditions, a race or a particular configuration. | Needs specific conditions, a race or a particular configuration. |
| Privileges required | LowThe attacker needs basic user privileges. | The attacker needs basic user privileges. |
| User interaction | NoneNo victim action needed. | No victim action needed. |
| Scope | UnchangedImpact stays within the vulnerable component. | Impact stays within the vulnerable component. |
| Confidentiality | HighTotal data disclosure possible. | Total data disclosure possible. |
| Integrity | HighComplete modification possible. | Complete modification possible. |
| Availability | HighFull outage possible. | Full outage possible. |
Common questions
Is CVE-2021-42287 being exploited?
Yes. CVE-2021-42287 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2021-42287?
CVE-2021-42287 is rated High with a CVSS score of 7.5. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2021-42287?
Yes. A fix has been recorded for CVE-2021-42287. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2021-42287 affect?
CVE-2021-42287 affects microsoft:windows_server_2004, microsoft:windows_server_2008, microsoft:windows_server_2012, microsoft:windows_server_2016, and 3 further products or versions. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
References
3 references in the CVE record, grouped by the tags the record gives them.
Patches (1)
- msrc.microsoft.com /update-guide/vulnerability/CVE-2021-42287
Other links (2)
- portal.msrc.microsoft.com /en-US/security-guidance/advisory/CVE-2021-42287
- cisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-42287
Where the data on this page comes from
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- PoC-in-GitHub: GitHub repositories that claim a proof of concept
Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.
Similar CVEs
Get CVEs like this by email. Join the free digest: the CVEs we flag as major, all CVSS 8.0 or higher, in up to three emails a day (sent at 05:00, 11:00 and 15:00 UTC). Matching alerts to the products you run needs an account, and accounts are invite-only during the beta.