Microsoft Windows Shell Protection Mechanism Failure Vulnerability
Microsoft Windows Shell contains a protection mechanism failure vulnerability that could allow an unauthorized attacker to bypass a security feature over a network.
- Vendor
- Microsoft
- Product
- Windows
- CVSS
- 8.8
- EPSS (exploit probability)
- 61.2%
- Status
- kev
- CISA patch-by (BOD 22-01)
- Added to KEV
Is CVE-2026-21510 being exploited?
Yes. CISA added CVE-2026-21510 to its Known Exploited Vulnerabilities catalog on . CISA only lists a CVE when it has reliable evidence of exploitation in the wild.
FIRST's EPSS model puts the probability of exploitation activity in the next 30 days at 61.2% (scored October 25, 2026).
- CISA KEV[ LISTED ]
- ENISA EUVD (exploited)[ — ]
- CIRCL KEV[ — ]
Catalog snapshot 2026-11-13. Full cross-catalog view: /kev-comparison
CVE-2026-21510 timeline
- Added to CISA KEVsame day as NVD
- Published to NVD
Every event links to its source. Catalog dates are each catalog's own; day offsets count from NVD publication. Data: JSON
What to do
CISA required actionApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
US federal civilian agencies must remediate by (21 days after listing) under BOD 22-01. Everyone else: that deadline is a sensible upper bound, not a target. Vendor guidance and the NVD record are linked under Source above.
Other Microsoft Windows CVEs we track
| CVE / Vulnerability | Severity | CVSS | EPSS | Added to KEV |
|---|---|---|---|---|
| CVE-2026-96951 Microsoft Windows Command Injection Vulnerability | [ HIGH ] | 8.8 | 9.8% | |
| CVE-2026-85880 Microsoft Windows ALPC Heap Buffer Overflow Privilege Escalationwrite-up | [ HIGH ] | 7.8 | 0.4% | |
| CVE-2026-81963 Microsoft Windows Update Stack Link-Following Privilege Escalationwrite-up | [ HIGH ] | 7.8 | 7.1% | |
| CVE-2026-68820 Windows AFD WinSock Use-After-Free Privilege Escalationwrite-up | [ HIGH ] | 7.0 | 8.6% | |
| CVE-2008-4250 Microsoft Windows Buffer Overflow Vulnerability | [ CRITICAL ] | 9.8 | 98.8% | |
| CVE-2026-32202 Microsoft Windows Protection Mechanism Failure Vulnerability | [ MEDIUM ] | 4.3 | 71.3% | |
| CVE-2025-60710 Microsoft Windows Link Following Vulnerabilityransomware use | [ HIGH ] | 7.8 | 4.6% | |
| CVE-2023-36424 Microsoft Windows Out-of-Bounds Read Vulnerability | [ HIGH ] | 7.8 | 12.1% |