Vulnerability intelligence
CVE-2026-21513
Microsoft MSHTML Framework Protection Mechanism Failure Vulnerability
Protection mechanism failure in MSHTML Framework allows an unauthorized attacker to bypass a security feature over a network.
CVSS Score
8.8
High
EPSS — Exploit Probability
16%
Riskier than 97% of all CVEs · checked 2026-10-17
Exploitation
Confirmed in the wild
KEV since 2026-02-10
Remediation
Patch available
Federal deadline 2026-03-03
CISA required action
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 federal agencies: 2026-03-03.
16 articles across 10 outlets · first covered Apr 8, 2026 · latest May 7, 2026
Associated threat actors
Coverage timeline
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Office and Windows flaws boost exploit kits in Q1 2026securelist.com · May 7, 2026
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Microsoft Warns of Active Exploit in CVE-2026-32202 Spoof Flawthehackernews.com · Apr 28, 2026
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APT28 exploits Windows SmartScreen gap for zero click LNK attackswww.securityweek.com · Apr 27, 2026
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Russia-linked APT28 uses PRISMEX to infiltrate Ukraine and allied infrastructure with advanced tacticssecurityaffairs.com · Apr 8, 2026
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APT28 Deploys New PRISMEX Malware Against Ukraine and NATO Alliesthehackernews.com · Apr 8, 2026
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Pawn Storm Campaign Deploys PRISMEX, Targets Government and Critical Infrastructure Entitieswww.trendmicro.com · Mar 26, 2026
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APT28 exploits MSHTML CVE-2026-21513 to run code via LNKsecurityaffairs.com · Mar 2, 2026
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MSHTML CVE-2026-21513 exploited by APT28; patch issuedthehackernews.com · Mar 2, 2026
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February 2026 Patch Tuesday: Six Active Zero-Days & 53 Other Flaws Addressedsocradar.io · Feb 11, 2026
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February 2026 Patch Tuesday includes six actively exploited zero-dayswww.malwarebytes.com · Feb 11, 2026
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U.S. CISA adds Microsoft Office and Microsoft Windows flaws to its Known Exploited Vulnerabilities catalogsecurityaffairs.com · Feb 11, 2026
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Patch Panic: Microsoft Fixes 6 Active Zero-Days in Feb 2026 Updatesecurityonline.info · Feb 11, 2026
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Microsoft Patch Tuesday security updates for February 2026 fix six actively exploited zero-dayssecurityaffairs.com · Feb 10, 2026
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Patch Tuesday, February 2026 Editionkrebsonsecurity.com · Feb 10, 2026
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Microsoft Patches 6 Actively Exploited Zero-Dayswww.darkreading.com · Feb 10, 2026
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6 Actively Exploited Zero-Days Patched by Microsoft With February 2026 Updateswww.securityweek.com · Feb 10, 2026