Is CVE-2021-29971 actively exploited?

No active exploitation of CVE-2021-29971 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2021-29971 be exploited remotely?

Yes. CVE-2021-29971 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2021-29971?

CVE-2021-29971 has a CVSS score of 9.8 (CRITICAL).

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CRITICAL

CVE-2021-29971

CWE-281Published: August 5, 2021· Updated: Jun 17, 2026

9.8

CVSS v3.1

Official Description

If a user had granted a permission to a webpage and saved that grant, any webpage running on the same host - irrespective of scheme or port - would be granted that permission. *This bug only affects Firefox for Android. Other operating systems are unaffected.*. This vulnerability affects Firefox < 90.

NVD Source

Technical Analysis

CVE-2021-29971 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.