CVE-2021-23984: mozilla firefox Authentication Bypass by Spoofing
Vulnerability summary
CVE-2021-23984 is a medium (CVSS 6.5) Authentication Bypass by Spoofing vulnerability in mozilla firefox. EPSS estimates a 1.11% chance of exploitation in the next 30 days, higher than 65.4% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 27 · Related 13Timeline
- 31-03-2021PublishedVulnerability first disclosed.
- 03-08-2024Last modifiedVulnerability information updated.
Description
A malicious extension could have opened a popup window lacking an address bar. The title of the popup lacking an address bar should not be fully controllable, but in this situation was. This could have been used to spoof a website and attempt to trick the user into providing credentials. This vulnerability affects Firefox ESR < 78.9, Firefox < 87, and Thunderbird < 78.9.
CVSS metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
- OSV · DebianEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
EPSS trend
Probability
1.11%
Chance of exploitation in the next 30 days
Percentile
65%
Versus all other CVEs
30-day change
0.00 pp
From 1.11% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Ubuntu6 products
- firefox< 87.0+build3-0ubuntu0.16.04.2 | < 87.0+build3-0ubuntu0.18.04.2 | < 87.0+build3-0ubuntu0.20.04.2
- mozjs38All versions (No fix recorded)
- mozjs52All versions (No fix recorded)
- mozjs68All versions (No fix recorded)
- mozjs78All versions (No fix recorded)
Mozilla3 products
- firefox≥ unspecified, < 87 | < 87.0
- firefox_esr≥ unspecified, < 78.9 | < 78.9
- thunderbird≥ unspecified, < 78.9 | < 78.9
Debian2 products
- firefox-esr< 78.9.0esr-1
- thunderbird< 1:78.9.0-1
3 vendors · 11 products
