What is the CVSS score of CVE-2021-26411?

CVE-2021-26411 has a CVSS 3.1 base score of 8.8 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L. EPSS exploitation probability: 92.5%.

Which versions of Microsoft are affected by CVE-2021-26411?

CVE-2021-26411 presents significant security risk, a use-after-free vulnerability rated CVSS 8.8.. A patch is available.

Is CVE-2021-26411 being actively exploited?

Yes, CVE-2021-26411 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, confirming active in-the-wild exploitation. Immediate patching is required.

How to fix or mitigate CVE-2021-26411?

Within 24 hours: Identify all affected systems and apply vendor patches immediately. If patching is delayed, consider network segmentation to limit exposure.

Microsoft CVE-2021-26411

HIGH

Use After Free (CWE-416)

2021-03-11 secure@microsoft.com

Buffer Overflow Use After Free Memory Corruption Microsoft

8.8

CVSS 3.1 · Vendor: microsoft

Severity by source

Vendor (microsoft) PRIMARY

8.8 HIGH

AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L

Primary rating from Vendor (microsoft) · only source for this CVE.

CVSS VectorVendor: microsoft

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

High

Availability

Low

Lifecycle Timeline

Analysis Generated

Mar 26, 2026 - 11:19 vuln.today

Added to CISA KEV

Oct 30, 2025 - 19:56 cisa

CISA KEV

Patch released

Oct 30, 2025 - 19:56 nvd

Patch available

CVE Published

Mar 11, 2021 - 16:15 nvd

HIGH 8.8

DescriptionCVE.org

Internet Explorer Memory Corruption Vulnerability

AnalysisAI

Internet Explorer contains a memory corruption vulnerability exploited by the Lazarus Group (North Korea) in campaigns targeting security researchers via social engineering and malicious websites in early 2021.

Technical ContextAI

The CWE-416 use-after-free in IE's rendering engine enables code execution when processing specially crafted HTML/JavaScript content. The exploit achieved reliable execution through heap manipulation techniques.