Threats / Microsoft / CVE-2026-21513
CVE-2026-21513
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Microsoft Windows vulnerability
Microsoft Windows MSHTML contains a protection mechanism failure allowing attackers to bypass security features over a network.
Verdict
Today item — known-exploited.
A protection mechanism failure in MSHTML enables security feature bypass via network attack. Active exploitation observed. CWE-693 indicates insufficient or missing security controls that could expose systems to unauthorized access or privilege escalation.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
15 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-02-10).
Probability (EPSS)
EPSS 0.15384 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Microsoft, Windows. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-693 Protection Mechanism Failure.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I identify that MSHTML's security mechanism is improperly implemented or absent, allowing me to craft a network request that circumvents the intended protection.
Business
Security controls fail to prevent unauthorized access, creating exposure to data breach, malware delivery, or system compromise through web-based attack vectors.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I deliver a malicious payload through a network channel that exploits the unprotected MSHTML processing to execute code or access restricted resources.
Business
Attackers gain foothold in enterprise environments, potentially leading to lateral movement, credential theft, or persistent compromise of Windows systems.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05