CVE-2021-21126

Name: CVE-2021-21126
Creator: NVD / NIST
Published: 2021-02-09T14:15:16.013+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 8.73%

Last modified Jun 17, 2026

CVE-2021-21126 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. Insufficient policy enforcement in extensions in Google Chrome prior to 88.0.4324.96 allowed a remote attacker to bypass site isolation via a crafted Chrome Extension.. EPSS estimates a 8.73% chance of exploitation in the next 30 days.

Description

Insufficient policy enforcement in extensions in Google Chrome prior to 88.0.4324.96 allowed a remote attacker to bypass site isolation via a crafted Chrome Extension.

Metrics

CVSS 3.1

6.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

EPSS Probability

8.73%

94.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-20

Affected Software

Vendor	Product	Versions
Google	Chrome	< 88.0.4324.96
Microsoft	Edge Chromium	< 88.0.705.50

References

https://chromereleases.googleblog.com/2021/01/stable-channel-update-for-desktop_19.htmlRelease Notes, Vendor Advisory
https://crbug.com/1108126Permissions Required, Third Party Advisory
https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-21126Third Party Advisory
https://chromereleases.googleblog.com/2021/01/stable-channel-update-for-desktop_19.htmlRelease Notes, Vendor Advisory
https://crbug.com/1108126Permissions Required, Third Party Advisory
https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-21126Third Party Advisory

Timeline

Published: Feb 9, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-21126?

Insufficient policy enforcement in extensions in Google Chrome prior to 88.0.4324.96 allowed a remote attacker to bypass site isolation via a crafted Chrome Extension.

How severe is CVE-2021-21126?

CVE-2021-21126 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 8.73% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21126?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-21126?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST