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TI-2021-06287 Aliases CVE-2021-23964GHSA-4j74-99vm-hh36

Out-of-bounds write in Mozilla Firefox

Priority MEDIUM 41CWE-787Published · Updated

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
Partial Red Hat: 9 fixed, 1 without a fix

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

Summary

Mozilla developers reported memory safety bugs present in Firefox 84 and Firefox ESR 78.6. 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 < 85, Thunderbird < 78.7, and Firefox ESR < 78.7.

Why it matters now

EPSS 0.01361 71st percentileScored 2026-11-07
Fix Partial Firefox (Mozilla): 85Thunderbird (Mozilla): 78.7+1 more productRed Hat: 8 advisoriesRed Hat: 9 fixed, 1 without a fix

SSVC decision points

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

Affected products

VendorProductAffected versionsFixed inStatusSource
MozillaFirefoxbefore 8585Patch availableCNA
MozillaThunderbirdbefore 78.778.7Patch availableCNA
MozillaFirefox ESRbefore 78.778.7Patch availableCNA
  • Firefox VendorMozilla Affected before 85 Fixed in 85 Patch available CNA
  • Thunderbird VendorMozilla Affected before 78.7 Fixed in 78.7 Patch available CNA
  • Firefox ESR VendorMozilla Affected before 78.7 Fixed in 78.7 Patch available CNA

CPE configurations NVD · 3

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*before 85.0VulnerableMozilla
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*before 78.7VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*before 78.7VulnerableMozilla
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions before 85.0 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:* Versions before 78.7 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions before 78.7 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Firefox (Mozilla) Fixed in 85
  • Fix · CNA Thunderbird (Mozilla) Fixed in 78.7
  • Fix · CNA Firefox ESR (Mozilla) Fixed in 78.7

Red Hat 8 advisories

  • RHSA-2021:0397 Released 2021-02-03 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.1) thunderbird-78.7.0-1.el8_1
  • RHSA-2021:0298 Released 2021-01-28 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 8) thunderbird-78.7.0-1.el8_3
  • RHSA-2021:0297 Released 2021-01-28 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux Client (v. 7) thunderbird-78.7.0-1.el7_9
    • Red Hat Enterprise Linux Server Optional (v. 7) thunderbird-78.7.0-1.el7_9
    • Red Hat Enterprise Linux Workstation (v. 7) thunderbird-78.7.0-1.el7_9
Show 5 more Red Hat advisories
  • RHSA-2021:0299 Released 2021-01-28 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.2) thunderbird-78.7.0-1.el8_2
  • RHSA-2021:0290 Released 2021-01-28 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux Client (v. 7) firefox-78.7.0-2.el7_9
    • Red Hat Enterprise Linux Client Optional (v. 7) firefox-78.7.0-2.el7_9
    • Red Hat Enterprise Linux Server (v. 7) firefox-78.7.0-2.el7_9
    • Red Hat Enterprise Linux Server Optional (v. 7) firefox-78.7.0-2.el7_9
    • Red Hat Enterprise Linux Workstation (v. 7) firefox-78.7.0-2.el7_9
    • Red Hat Enterprise Linux Workstation Optional (v. 7) firefox-78.7.0-2.el7_9
  • RHSA-2021:0288 Released 2021-01-27 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream (v. 8) firefox-78.7.0-2.el8_3
  • RHSA-2021:0289 Released 2021-01-27 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.2) firefox-78.7.0-2.el8_2
  • RHSA-2021:0285 Released 2021-01-27 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.1) firefox-78.7.0-2.el8_1

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2021:0288, RHSA-2021:0298
Red Hat Enterprise Linux AppStream EUS (v. 8.1)Fixed RHSA-2021:0285, RHSA-2021:0397
Red Hat Enterprise Linux AppStream EUS (v. 8.2)Fixed RHSA-2021:0289, RHSA-2021:0299
Red Hat Enterprise Linux Client (v. 7)Fixed RHSA-2021:0290, RHSA-2021:0297
Red Hat Enterprise Linux Client Optional (v. 7)Fixed RHSA-2021:0290
Red Hat Enterprise Linux Server (v. 7)Fixed RHSA-2021:0290
Red Hat Enterprise Linux Server Optional (v. 7)Fixed RHSA-2021:0290, RHSA-2021:0297
Red Hat Enterprise Linux Workstation (v. 7)Fixed RHSA-2021:0290, RHSA-2021:0297
Red Hat Enterprise Linux Workstation Optional (v. 7)Fixed RHSA-2021:0290

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-23964
  2. 2026-10-03 Alias added: GHSA-4j74-99vm-hh36

References

Advisory 4

  • 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