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Known exploited · Google

CVE-2021-37973: Google Chromium Portals Use-After-Free Vulnerability

What it is

Google Chromium Portals contains a use-after-free vulnerability that allows a remote attacker, who has compromised the renderer process, to potentially perform a sandbox escape via a crafted HTML page. This vulnerability affects web browsers that utilize Chromium, including Google Chrome and Microsoft Edge.

Added November 3, 2021Due November 17, 2021CISA KEV catalog 2026.10.01

Vendor
Google
Product
Chromium Portals
Added to KEV
November 3, 2021
CISA due date
November 17, 2021
Ransomware use
Unknown

What CISA requires

Apply updates per vendor instructions.

Forensic triage

No

What to do now

  1. Find every instance of Chromium Portals you run, including the forgotten ones, and check its version against the vendor advisory.
  2. Apply the vendor's fix or mitigation, before November 17, 2021 if you are bound by CISA's deadline, sooner if it faces the internet.
  3. Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.

References

CVE-2021-37973 in the National Vulnerability Database

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Source: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.