Is CVE-2021-21166 actively exploited?

Yes. CVE-2021-21166 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, which means exploitation in the wild has been confirmed.

Can CVE-2021-21166 be exploited remotely?

The attack vector of CVE-2021-21166 has not been classified yet.

What is the CVSS score of CVE-2021-21166?

CVE-2021-21166 has not received a CVSS score yet.

HOME VULNERABILITIESCVE-2021-21166

HIGHCISA KEVIN THE WILD

CVE-2021-21166

Published: November 3, 2021

EPSS:36.26%probability of exploitation in 30 daysPercentile:97.0th

Official Description

Google Chromium contains a race condition vulnerability that allows a remote attacker to potentially exploit heap corruption via a crafted HTML page. This vulnerability could affect multiple web browsers that utilize Chromium, including, but not limited to, Google Chrome, Microsoft Edge, and Opera.

NVD Source

CISA KEV Advisory

Google Chromium Race Condition Vulnerability

Added to KEV: 2021-11-03Federal patch deadline: 2021-11-17

Required Action (CISA)

Apply updates per vendor instructions.

Risk Analysis

This Google Chromium vulnerability is a race condition that can lead to heap corruption via a crafted HTML page, potentially affecting multiple web browsers. Its confirmed exploitation by CISA (is_in_kev: true) and high EPSS score of 0.36262 indicate a significant and urgent risk for users of Chromium-based browsers.

This vulnerability is actively being exploited in the wild and is part of the CISA Known Exploited Vulnerabilities Catalog. This confirms that attackers are successfully leveraging this flaw via crafted HTML pages.

Recommended Action

Update all Chromium-based web browsers, such as Google Chrome, Microsoft Edge, and Opera, to the latest available versions. Exercise caution when visiting untrusted websites.

Generated by the CTIWATCH analysis pipeline from this CVE's metadata (CVSS, EPSS, KEV status, exploit intelligence). Verify against vendor advisories before acting.

Technical Analysis

CVE-2021-21166 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

CISA has added CVE-2021-21166 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.