CVE-2021-23979: mozilla firefox Out-of-bounds Write
Vulnerability summary
CVE-2021-23979 is a high (CVSS 8.8) Out-of-bounds Write vulnerability in mozilla firefox. EPSS estimates a 0.92% chance of exploitation in the next 30 days, higher than 59.7% of scored vulnerabilities. 1 public exploit is recorded.
Advisory lineage
Upstream 0 · Downstream 3 · Related 3Timeline
- 26-02-2021PublishedVulnerability first disclosed.
- 03-08-2024Last modifiedVulnerability information updated.
Description
Mozilla developers reported memory safety bugs present in Firefox 85. 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 < 86.
CVSS metrics
3 scores · 2 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
EPSS trend
Probability
0.92%
Chance of exploitation in the next 30 days
Percentile
60%
Versus all other CVEs
30-day change
0.00 pp
From 0.92% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
1 foundExploit Reference (bugzilla.mozilla.org)
Maturity: unknown
Weaknesses
CWE · root causeAffected systems
Ubuntu5 products
- firefox< 86.0+build3-0ubuntu0.16.04.1 | < 86.0+build3-0ubuntu0.18.04.1 | < 86.0+build3-0ubuntu0.20.04.1
- mozjs38All versions (No fix recorded)
- mozjs52All versions (No fix recorded)
- mozjs68All versions (No fix recorded)
- mozjs78All versions (No fix recorded)
Mozilla1 product
- firefox< 86 | < 86.0
2 vendors · 6 products