Microsoft · Windows
CVE-2026-21513
MSHTML Framework Security Feature Bypass Vulnerability
What it is
Protection mechanism failure in MSHTML Framework allows an unauthorized attacker to bypass a security feature over a network.
CISA: Microsoft MSHTML Framework contains a protection mechanism failure vulnerability that could allow an unauthorized attacker to bypass a security feature over a network.
What to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Deadline for US federal agencies: March 3, 2026
More exploited flaws from Microsoft
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Oct 13, 2026 | Command Injection | Windows | High 8.8 | 9.8% |
| Sep 8, 2026 | Link Following | Windows | High 7.8 | 0.4% |
| Sep 8, 2026 | Heap-Based Buffer Overflow | Windows | High 7.8 | 0.4% |
| May 20, 2026 | Buffer Overflow | Windows | Critical 9.8 | 99% |
| Apr 28, 2026 | Protection Mechanism Failure | Windows | Medium 4.3 | 71% |
| Apr 13, 2026 | Out-of-Bounds Read | Windows | High 7.8 | 12% |
| Apr 13, 2026 | Link Following | Windows | High 7.8 | 4.6% |
| Feb 17, 2026 | Microsoft Windows Video ActiveX Control Remote Code Execution | Windows | High 8.8 | 77% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.