SOC status:Duty analyst on shift

UK Cyber Defence
VulnerabilityModified

CVE-2021-23996

This vulnerability affects Firefox < 88.

MEDIUM 6.5EPSS 0.72%

Does this matter?

Lower severity and a low EPSS score (0.72%). Track it; it rarely justifies an emergency change on its own.

Description

By utilizing 3D CSS in conjunction with Javascript, content could have been rendered outside the webpage's viewport, resulting in a spoofing attack that could have been used for phishing or other attacks on a user. This vulnerability affects Firefox < 88.

CVSS 3.1
6.5 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
EPSS
0.72% probability · 54th percentile
Public exploits
None in Exploit-DB
CISA KEV
Not listed
Affected
mozilla/firefox
Source
security@mozilla.org
EPSS trend
0%3%5%26 October 2026: 0.72%26 October 202626 October 2026

EPSS 0.7% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.