CVE-2021-29987

Name: CVE-2021-29987
Creator: NVD / NIST
Published: 2021-08-17T20:15:07.973+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 0.95%

Last modified Jun 17, 2026

CVE-2021-29987 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. After requesting multiple permissions, and closing the first permission panel, subsequent permission panels will be displayed in a different position but still record a click in the default location, making it possible to trick a user into accepting a permission they did not want to. *This bug only affects Firefox on Linux. EPSS estimates a 0.95% chance of exploitation in the next 30 days.

Description

After requesting multiple permissions, and closing the first permission panel, subsequent permission panels will be displayed in a different position but still record a click in the default location, making it possible to trick a user into accepting a permission they did not want to. *This bug only affects Firefox on Linux. Other operating systems are unaffected.*. This vulnerability affects Firefox < 91 and Thunderbird < 91.

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

0.95%

56.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-307

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 91.0
Mozilla	Thunderbird	< 91.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1716129Issue Tracking, Vendor Advisory
https://security.gentoo.org/glsa/202202-03Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2021-33/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-36/Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1716129Issue Tracking, Vendor Advisory
https://security.gentoo.org/glsa/202202-03Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2021-33/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-36/Vendor Advisory

Timeline

Published: Aug 17, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-29987?

How severe is CVE-2021-29987?

CVE-2021-29987 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.95% probability of exploitation in the next 30 days.

How do I fix CVE-2021-29987?

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-2021-29987?

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

Scan your code now

Source: NVD / NIST