CVE-2021-23986: mozilla firefox Origin Validation Error
Vulnerability summary
CVE-2021-23986 is a medium (CVSS 6.5) Origin Validation Error vulnerability in mozilla firefox. EPSS estimates a 0.43% chance of exploitation in the next 30 days, higher than 36.3% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 3 · Related 3Timeline
- 31-03-2021PublishedVulnerability first disclosed.
- 03-08-2024Last modifiedVulnerability information updated.
Description
A malicious extension with the 'search' permission could have installed a new search engine whose favicon referenced a cross-origin URL. The response to this cross-origin request could have been read by the extension, allowing a same-origin policy bypass by the extension, which should not have cross-origin permissions. This cross-origin request was made without cookies, so the sensitive information disclosed by the violation was limited to local-network resources or resources that perform IP-based authentication. This vulnerability affects Firefox < 87.
CVSS metrics
3 scores · 2 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
EPSS trend
Probability
0.43%
Chance of exploitation in the next 30 days
Percentile
36%
Versus all other CVEs
30-day change
0.00 pp
From 0.43% 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
Ubuntu5 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)
Mozilla1 product
- firefox≥ unspecified, < 87 | < 87.0
2 vendors · 6 products
References
6 links- bugzilla.mozilla.org/show_bug.cgi?id=1692623X Refsource MISCIssue TrackingPermissions RequiredVendor Advisory