CVE-2021-23987: mozilla firefox Out-of-bounds Write
Vulnerability summary
CVE-2021-23987 is a high (CVSS 8.8) Out-of-bounds Write vulnerability in mozilla firefox. EPSS estimates a 1.42% chance of exploitation in the next 30 days, higher than 72.3% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 27 · Related 13Timeline
- 31-03-2021PublishedVulnerability first disclosed.
- 03-08-2024Last modifiedVulnerability information updated.
Description
Mozilla developers and community members reported memory safety bugs present in Firefox 86 and Firefox ESR 78.8. 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 ESR < 78.9, Firefox < 87, and Thunderbird < 78.9.
CVSS metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated8.8HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated8.8HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS trend
Probability
1.42%
Chance of exploitation in the next 30 days
Percentile
72%
Versus all other CVEs
30-day change
0.00 pp
From 1.42% 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
References
13 links- bugzilla.mozilla.org/buglist.cgi?bug_id=1513519%2C1683439%2C1690169%2C1690718X Refsource MISCIssue TrackingPatchVendor Advisory
