CVE-2021-29966

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-06-24 · updated 2026-06-17
Weakness: CWE-787

Description

Mozilla developers reported memory safety bugs present in Firefox 88. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 89.

Affected products

Mozilla Firefox: from 78.11.0 before 89.0 — fixed in 89.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 89.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/buglist.cgi?bug_id=1660307%2C1686154%2C1702948%2C1708124
https://security.gentoo.org/glsa/202107-09
https://www.mozilla.org/security/advisories/mfsa2021-23/
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1660307%2C1686154%2C1702948%2C1708124
https://security.gentoo.org/glsa/202107-09
https://www.mozilla.org/security/advisories/mfsa2021-23/

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