CVE-2026-21513
Published: February 10, 2026
Official Description
Microsoft MSHTML Framework contains a protection mechanism failure vulnerability that could allow an unauthorized attacker to bypass a security feature over a network.
CISA KEV Advisory
Microsoft MSHTML Framework Protection Mechanism Failure Vulnerability
Microsoft MSHTML Framework contains a protection mechanism failure vulnerability that could allow an unauthorized attacker to bypass a security feature over a network.
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Risk Analysis
This critical vulnerability in Microsoft MSHTML Framework allows an unauthenticated attacker to bypass security features over a network, potentially leading to full system compromise. With a CVSS score of 8.8, it is rated as HIGH severity, and its presence in CISA's KEV catalog with an EPSS score of 0.04119 highlights its urgency.
This vulnerability is actively being exploited in the wild, as confirmed by its presence in CISA's KEV catalog. It is remotely exploitable with low attack complexity, requiring user interaction.
Apply the latest security updates for Microsoft products that utilize the MSHTML Framework. Implement robust network segmentation and user awareness training to reduce the risk of successful exploitation.
Technical Analysis
CVE-2026-21513 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.
A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 8.8.
CISA has added CVE-2026-21513 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
News & Research Mentioning CVE-2026-21513
A recently disclosed security flaw patched by Microsoft may have been exploited by the Russia-linked state-sponsored threat actor known as APT28, according to new findings from Akamai. The vulnerability in question is CVE-2026-21513 (CVSS score: 8.8), a high-severity security feature bypass affecting the MSHTML Framework. "Protection mechanism failure in MSHTML Framework allows an unauthorized [xlite_meta score:59 src:The Hacker News xlite_fp:f8be4c9f1de4b66086f88e2df0625a702d7354234e2e61762a3f5ee647e4a17f]
CISA has added six new vulnerabilities to its Known Exploited Vulnerabilities (KEV) Catalog, based on evidence of active exploitation. CVE-2026-21510 Microsoft Windows Shell Protection Mechanism Failure Vulnerability CVE-2026-21513 Microsoft MSHTML Framework Security Feature Bypass Vulnerability CVE-2026-21514 Microsoft Office Word Reliance on Untrusted Inputs in a Security Decision Vulnerability CVE-2026-21519 Microsoft Windows Type Confusion Vulnerability CVE-2026-21525 Microsoft Windows NULL Pointer Dereference Vulnerability CVE-2026-21533 Windows Remote Desktop Services Elevation of Privilege Vulnerability These types of vulnerabilities are frequent attack vectors for malicious cyber actors and pose significant risks to the federal enterprise. Bi [xlite_meta score:53 src:CISA Alerts xlite_fp:88d5ff4976309c17f8264912552cef85549f24eb7de38b00c6011d2454de9f37]
All References (2)
Quick Facts
Known Threat Actors
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2026-21513 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
- !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
- !Active exploitation confirmed — treat as P1