CVE-2021-29955

Name: CVE-2021-29955
Creator: NVD / NIST
Published: 2021-06-24T14:15:10.053+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.3/10EPSS 1.52%

Last modified Jun 17, 2026

CVE-2021-29955 is a medium-severity vulnerability rated 5.3/10 on the CVSS scale. A transient execution vulnerability, named Floating Point Value Injection (FPVI) allowed an attacker to leak arbitrary memory addresses and may have also enabled JIT type confusion attacks. (A related vulnerability, Speculative Code Store Bypass (SCSB), did not affect Firefox.). EPSS estimates a 1.52% chance of exploitation in the next 30 days.

Description

A transient execution vulnerability, named Floating Point Value Injection (FPVI) allowed an attacker to leak arbitrary memory addresses and may have also enabled JIT type confusion attacks. (A related vulnerability, Speculative Code Store Bypass (SCSB), did not affect Firefox.). This vulnerability affects Firefox ESR < 78.9 and Firefox < 87.

Metrics

CVSS 3.1

5.3/10

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

EPSS Probability

1.52%

71.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-74

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 87.0
Mozilla	Firefox Esr	< 78.9

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1692972Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-10/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-11/Release Notes, Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1692972Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-10/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-11/Release Notes, Vendor Advisory

Timeline

Published: Jun 24, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-29955?

How severe is CVE-2021-29955?

CVE-2021-29955 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 1.52% probability of exploitation in the next 30 days.

How do I fix CVE-2021-29955?

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-2021-29955?

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

Scan your code now

Source: NVD / NIST