Microsoft Internet Explorer Use-After-Free Vulnerability
What it is
Use-after-free vulnerability in Microsoft Internet Explorer allows remote attackers to execute remote code via a crafted web site that triggers access to a deleted object.
Known to be used in ransomware campaigns.Active threat actors have chained this vulnerability into ransomware operations — treat patching as a same-week priority, not a "next maintenance window" task. The coping action is the same one below; the urgency is higher.
Who's affected
Affects anyone running Microsoft Internet Explorer. Microsoft products in a small practice typically sit close to credentials, email, or document workflows — treat the patch as in-scope.
What to do
Apply updates per vendor instructions.
CISA action deadline: April 18, 2022. Federal agencies must complete the required action by this date. For private SMBs the deadline is advisory — but treat it as a strong recommendation, especially if you handle regulated data (HIPAA, GLBA, ABA model rules).
If you don't have someone in-house to verify the patch deployed across every endpoint — or you're not sure whether you're affected — that's exactly the kind of triage we do. Book a free 20-minute triage call.
Severity
CVSS base score: 8.8 — HIGH
Weakness classification: CWE-416
Source
Pulled daily from the public cisagov/kev-data mirror (CC0). View the original entry on cisa.gov. CISA KEV is US-Government public-domain data; we add the SMB-vertical framing and the coping action above.