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CVE-2026-21513 is a protection mechanism failure in Microsoft MSHTML that allows a remote, unauthenticated attacker to bypass file-execution security prompts. The vulnerability affects hyperlink navigation in the Internet Explorer frame library, specifically the _AttemptShellExecuteForHlinkNavigate function, where insufficient validation of navigation parameters permits execution of local or remote resources outside the intended browser security context. Exploitation typically involves convincing a user to open a crafted HTML file or Windows shortcut. The vulnerability was exploited as a zero-day by APT28 and was patched on February 10, 2026.
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No public exploit code observed for this vulnerability.
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179 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Microsoft MSHTML/ieframe.dll security feature bypass vulnerability involving hyperlink navigation validation flaws that can reach ShellExecuteExW and execute local or remote resources outside the intended browser security context.
A zero-day vulnerability in the Microsoft MSHTML framework's handling of hyperlinks in ieframe.dll that can be triggered via a crafted .lnk file embedding HTML content.
An MSHTML security bypass vulnerability identified as one of the CVEs being tested by the malware delivery infrastructure.
A specific vulnerability referenced only as smaller test material in the exposed lab; no technical details are provided in the content.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.