Microsoft Internet Explorer Use-After-Free Vulnerability
CVE-2010-0249 is a security vulnerability in Microsoft Internet Explorer, added to CISA KEV on May 20, 2026. Patch priority: Plan to patch.
What it is
Microsoft Internet Explorer contains an use-after-free vulnerability that could allow remote attackers to execute arbitrary code by accessing a pointer associated with a deleted object. The impacted product could be end-of-life (EoL) and/or end-of-service (EoS). Users should discontinue product utilization.
VulnCheck tracked exploitation 5969 days before CISA's KEV listing. VulnCheck's broader catalog of in-the-wild exploitation evidence picked this up before it landed on CISA's formal list. Per-CVE fact about this entry; not a population claim about lead time in general.
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 mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
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.
Insurance readiness
Your insurer will ask if this is patched.
Unpatched entries on CISA's Known Exploited Vulnerabilities list are exactly what cyber-insurance carrier questionnaires probe for, and knowing which controls they check is how you keep a renewal from stalling.
Get the free carrier questionnaire →Severity
CVSS base score: 8.8 — HIGH
Weakness classification: CWE-416
CISA due date
Federal deadline: June 3, 2026. 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).
EPSS
EPSS score: 91.9% — higher than 100% of all scored CVEs.
EPSS estimates the probability of exploitation activity in the next 30 days. Every entry on this site is already confirmed exploited, so read it as relative urgency among the things you still have open, not as permission to wait.
Other exploited Microsoft Internet Explorer entries
More CISA KEV entries for Microsoft Internet Explorer. Same product line, same actively-exploited status.
Source
This entry comes from CISA's Known Exploited Vulnerabilities catalog, public US-Government data we pull daily. The plain-language framing and the what-to-do guidance above are ours. View the original entry on cisa.gov.