Yes. CISA added CVE-2021-40450 to its Known Exploited Vulnerabilities catalogue on 25 April 2022, which it does only when there is reliable evidence of active exploitation. CISA has not linked it to known ransomware campaigns. Microsoft Win32k contains an unspecified vulnerability that allows for privilege escalation. Any organisation running the affected product should treat remediation as urgent.
How to interpret “being exploited in the wild” for this CVE
For a vulnerability question like this, the key distinction is between theoretical exposure and confirmed abuse. The CISA KEV catalogue is the operational signal that matters most here: once a CVE is listed, the issue is no longer just a candidate risk, it is treated as active exploitation with real-world priority. For the microsoft win32k privilege escalation issue, that changes the response from routine patch planning to urgent remediation.
That urgency is especially important for privilege escalation flaws because they often sit behind an initial foothold rather than acting as the entry point themselves. In practice, attackers may use phishing, a second vulnerability, or stolen access to land on a host first, then use the Win32k flaw to gain higher privileges and expand control. CISA Known Exploited Vulnerabilities Catalog is the authoritative place to confirm the active-exploitation status and required remediation posture.
When a Windows kernel component is involved, privilege escalation can quickly turn a limited compromise into system-level access. That is why the correct question is not only whether exploitation is happening, but what an attacker could do after exploitation succeeds: disable defenses, dump credentials, move laterally, or stage additional payloads. MITRE ATT&CK Enterprise Matrix is useful here because it frames privilege escalation as part of a larger post-compromise sequence rather than an isolated bug.
What to do if you think you are exposed
Confirm whether the affected Microsoft product is present anywhere in your environment, including older endpoints, build systems, VDI pools, and unmanaged assets. For exploited CVEs, asset visibility matters as much as patch velocity, because untracked systems are usually the ones that miss the response window. If the vulnerable component exists, treat it as a live remediation item, not a backlog candidate.
The practical workflow is straightforward: identify exposure, apply the vendor fix or the CISA-required action, then verify that the vulnerable build is no longer reachable on any in-scope system. For exploited vulnerabilities, normal change cadence is often too slow, so emergency maintenance windows, compensating controls, and temporary isolation may be justified while remediation is staged. NIST National Vulnerability Database is useful for tracking the canonical CVE record alongside vendor advisories.
If patching must wait, reduce exposure by limiting administrative access, constraining reachable hosts, and watching for suspicious privilege changes. A privilege escalation flaw is most dangerous when it can be chained with weak segmentation or standing admin rights, so the interim goal is to shrink blast radius until the fix is deployed. Vulnerability Management Guide is a good reference point for KEV-driven prioritisation, exception handling, and verification.
What to check for earlier compromise and post-fix cleanup
When exploitation is confirmed in the wild, the response should include compromise assessment, not just patching. Review authentication logs, privilege elevation events, new local administrators, unusual scheduled tasks, service creation, suspicious DLL loading, and evidence of defense tampering. If the exploit was used to gain higher privilege, the real impact may be in what happened after the elevation, not in the exploitation event itself.
Credential hygiene also matters if the elevated host had access to secrets, tokens, or admin sessions. A successful privilege escalation can expose cached credentials and privileged sessions, so rotation may be necessary even when the original vulnerability has been fixed. Privileged Access Management Guide is relevant because it ties post-compromise cleanup to session control, vaulting, and privilege review.
Risk and Threat Considerations
This kind of flaw is dangerous because privilege escalation changes the attacker’s options after the first foothold. Even if initial access was limited, a successful exploit can convert that foothold into administrative control, which increases the chance of persistence, defense evasion, and lateral movement.
Failure mechanism: An attacker uses an existing foothold to trigger the Win32k privilege escalation, then uses the higher privilege level to tamper with security controls, access sensitive data, or stage follow-on activity.
Impact: The practical impact can include full host compromise, broader internal movement, exposure of credentials or secrets, and faster operational disruption than a non-elevating vulnerability would normally allow.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
MITRE ATT&CK addresses the attack and risk surface, while CIS Controls v8, NIST SP 800-53 Rev 5 and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| CIS Controls v8 | CIS-7 — Continuous Vulnerability Management | The CVE requires urgent prioritization, remediation, and verification. |
| Recommendation — Prioritize and verify remediation for KEV-listed exposures across all in-scope assets. | ||
| NIST SP 800-53 Rev 5 | RA-5 — Vulnerability Monitoring and Scanning | Confirm exposure and track remediation for the exploited Win32k flaw. |
| SI-2 — Flaw Remediation | An actively exploited vulnerability needs urgent patching and verification. | |
| Recommendation — Scan for the affected software, confirm exposure, and track remediation to closure. Apply the vendor fix quickly and verify vulnerable instances are removed. | ||
| MITRE ATT&CK | T1068 — Exploitation for Privilege Escalation | This CVE is explicitly a privilege escalation issue used in post-exploit chaining. |
| Recommendation — Map telemetry to privilege-escalation activity and hunt for follow-on abuse. | ||
| NIST CSF 2.0 | PR.IP-12 — Vulnerability Management Plan | KEV-driven response belongs in a formal vulnerability management process. |
| Recommendation — Use a prioritized vulnerability process to accelerate remediation of exploited CVEs. | ||
Practitioner Guidance
What to prioritise: Prioritise systems where the vulnerable Microsoft product is internet-facing, user-accessible, or already operating with elevated local rights. Those systems have the shortest path from exploit to meaningful impact.
What to verify: Verify that remediation is complete across all endpoints, not just the primary estate. For exploited CVEs, one unpatched workstation or server can be enough to reopen the attack path.
Practitioner takeaway: Treat KEV-listed privilege escalation flaws as active incident-response items, because the main question is no longer whether exploitation is possible, but whether an attacker can still turn a foothold into control.
Related resources from NHI Mgmt Group
- Guide: Zero-Day and Exploited Vulnerabilities Guide
- Is CVE-2021-31201 (Microsoft Enhanced Cryptographic Provider Privilege Escalation) being exploited in the wild?
- Is CVE-2021-31199 (Microsoft Enhanced Cryptographic Provider Privilege Escalation) being exploited in the wild?
- Is CVE-2021-42287 (Microsoft Active Directory Domain Services Privilege Escalation) being exploited in the wild?
- Is CVE-2021-42278 (Microsoft Active Directory Domain Services Privilege Escalation) being exploited in the wild?