Threats / Microsoft / CVE-2021-26411
CVE-2021-26411
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Microsoft Internet Explorer vulnerability
Microsoft Internet Explorer use-after-free vulnerability enabling memory corruption. Actively exploited in ransomware campaigns with high exploitation likelihood.
Verdict
Today item, not a backlog item.
Use-after-free flaw in Internet Explorer permits memory corruption attacks. High EPSS score and confirmed wild exploitation tied to ransomware operations indicate imminent threat requiring immediate patching.
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 2021-11-03), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.81103 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Microsoft, Internet Explorer. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-416 Use After Free — weakness family: Memory safety.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 craft a malicious webpage or email attachment that triggers the use-after-free condition in Internet Explorer's memory management.
Business
Employee browsing compromised or attacker-controlled web content becomes initial infection vector for ransomware deployment.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I achieve arbitrary code execution through memory corruption, establishing foothold on the victim's system with user privileges.
Business
Attacker gains persistent access to corporate network, enabling lateral movement and reconnaissance.
3
Lateral reach — past segmentation narrative 3
Attacker
I escalate privileges and deploy ransomware payload across networked systems.
Business
Critical business systems encrypted, operations halted, and ransom demanded with threat of data exfiltration.
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