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Security advisories | Mar 09, 2021

Browser Zero-Day Vulnerability

THE THREAT

In the March Microsoft Patch Tuesday release, Microsoft disclosed an actively exploited zero-day vulnerability impacting the Edge (EdgeHTML-based) and Internet Explorer (versions 9 & 11) web-browsers. The vulnerability is tracked as CVE-2021-26411 and received a criticality score of 8.8/10. If exploited, the vulnerability allows for Remote Code Execution (RCE).

Organizations are strongly recommended to apply the security patches provided by Microsoft, as attacks have been identified in the wild.

What we’re doing about it

  • MVS will automatically add the relevant plugins for CVE-2021-26411 once details are made available
  • eSentire security teams continue to track this topic for additional details and detection opportunities

What you should do about it

  • After performing a business impact review, apply the relevant security patches provided by Microsoft

Additional information

Details of real-world attacks involving CVE-2021-26411 have not been shared. It is currently unclear how widespread exploitation is of the vulnerability.

In an attack scenario, a threat actor could either host their own malicious page or compromise another website. Users visiting the malicious page from a vulnerable browser will result in the compromise. The only required user interaction is viewing the malicious page, making this an ideal vulnerability for drive-by exploit attacks.

Vulnerable Products:

  • Microsoft Edge (EdgeHTML-based)
  • Internet Explorer 11
  • Internet Explorer 9

References:

[1] https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-26411