TI-2021-06300 Aliases CVE-2021-23979 GHSA-h2wp-qp38-rjj4

Out-of-bounds write in Mozilla Firefox

MEDIUM 40CWE-787Published 2021-02-26 · Updated 2024-08-03

Key facts

Attack vector: Network
Privileges required: None
User interaction: Required
Attack complexity: Low
Impact type: Code execution
Confidentiality · integrity · availability: High · High · High
Fix status: Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-787 and the CVSS impact.

Summary

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.

Why it matters now

EPSS 0.00925 60th percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by NVD

Fix Fixed Firefox (Mozilla): 86

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
Mozilla	Firefox	before 86	86	Patch available	CNA

Firefox VendorMozilla Affected before 86 Fixed in 86 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:mozilla:firefox::::::::	before 86.0	Vulnerable	Mozilla

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions before 86.0 Vulnerable ·Mozilla

Remediation

Fix · CNA Firefox (Mozilla) Fixed in 86

Timeline

2026-10-02 Threatist record created from CVE-2021-23979
2026-10-03 Alias added: GHSA-h2wp-qp38-rjj4

References

Exploit 1

https://bugzilla.mozilla.org/buglist.cgi?bug_id=1663222%2C1666607%2C1672120%2C1678463%2C1678927%2C1679560%2C1681297%2C1681684%2C1683490%2C1684377%2C1684902

Advisory 1

https://www.mozilla.org/security/advisories/mfsa2021-07/

TI-2024-08981 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.8
TI-2022-09832 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.6
TI-2019-08769 Improper input validation in Mozilla Firefox ESR KEVCVSS 3.1CRITICAL 10.0
TI-2010-03577 Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before… KEVCVSS 3.1CRITICAL 9.8
TI-2023-04799 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
TI-2023-04477 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8

See all 3444 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences