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TI-2021-03005 Aliases CVE-2021-4129GHSA-v25r-h4v7-62rr

Out-of-bounds write in Mozilla Firefox

Priority MEDIUM 51CWE-787Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 10 fixed, 1 without a fix

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

Summary

Mozilla developers and community members Julian Hector, Randell Jesup, Gabriele Svelto, Tyson Smith, Christian Holler, and Masayuki Nakano reported memory safety bugs present in Firefox 94. 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 < 95, Firefox ESR < 91.4.0, and Thunderbird < 91.4.0.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.01062 64th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial Firefox (Mozilla): 95Firefox ESR (Mozilla): 91.4.0+1 more productRed Hat: 10 advisoriesRed Hat: 10 fixed, 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MozillaFirefoxbefore 9595Patch availableCNA
MozillaFirefox ESRbefore 91.4.091.4.0Patch availableCNA
MozillaThunderbirdbefore 91.4.091.4.0Patch availableCNA
  • Firefox VendorMozilla Affected before 95 Fixed in 95 Patch available CNA
  • Firefox ESR VendorMozilla Affected before 91.4.0 Fixed in 91.4.0 Patch available CNA
  • Thunderbird VendorMozilla Affected before 91.4.0 Fixed in 91.4.0 Patch available CNA

CPE configurations NVD · 3

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*before 95.0VulnerableMozilla
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*before 91.4.0VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*before 91.4.0VulnerableMozilla
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions before 95.0 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:* Versions before 91.4.0 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions before 91.4.0 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Firefox (Mozilla) Fixed in 95
  • Fix · CNA Firefox ESR (Mozilla) Fixed in 91.4.0
  • Fix · CNA Thunderbird (Mozilla) Fixed in 91.4.0

Red Hat 10 advisories

  • RHSA-2021:5055 Released 2021-12-09 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v. 8.1) thunderbird-91.4.0-2.el8_1
  • RHSA-2021:5046 Released 2021-12-09 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux Client (v. 7) thunderbird-91.4.0-3.el7_9
    • Red Hat Enterprise Linux Server Optional (v. 7) thunderbird-91.4.0-3.el7_9
    • Red Hat Enterprise Linux Workstation (v. 7) thunderbird-91.4.0-3.el7_9
  • RHSA-2021:5048 Released 2021-12-09 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v.8.4) thunderbird-91.4.0-2.el8_4
Show 7 more Red Hat advisories
  • RHSA-2021:5045 Released 2021-12-09 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 8) thunderbird-91.4.0-2.el8_5
  • RHSA-2021:5047 Released 2021-12-09 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.2) thunderbird-91.4.0-2.el8_2
  • RHSA-2021:5014 Released 2021-12-08 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux Client (v. 7) firefox-91.4.0-1.el7_9
    • Red Hat Enterprise Linux Client Optional (v. 7) firefox-91.4.0-1.el7_9
    • Red Hat Enterprise Linux Server (v. 7) firefox-91.4.0-1.el7_9
    • Red Hat Enterprise Linux Server Optional (v. 7) firefox-91.4.0-1.el7_9
    • Red Hat Enterprise Linux Workstation (v. 7) firefox-91.4.0-1.el7_9
    • Red Hat Enterprise Linux Workstation Optional (v. 7) firefox-91.4.0-1.el7_9
  • RHSA-2021:5016 Released 2021-12-08 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.2) firefox-91.4.0-1.el8_2
  • RHSA-2021:5015 Released 2021-12-08 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v.8.4) firefox-91.4.0-1.el8_4
  • RHSA-2021:5013 Released 2021-12-08 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream (v. 8) firefox-91.4.0-1.el8_5
  • RHSA-2021:5017 Released 2021-12-08 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream E4S (v. 8.1) firefox-91.4.0-1.el8_1

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    Mozilla Firefox 95

    2 records Highest priority Priority MEDIUM 2 MEDIUM

    Other records, highest priority first

    • TI-2021-03004 Use after free in Mozilla FirefoxPriority MEDIUM 62
    Show all 2 records →

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-2021:5013, RHSA-2021:5045
Red Hat Enterprise Linux AppStream E4S (v. 8.1)Fixed RHSA-2021:5017, RHSA-2021:5055
Red Hat Enterprise Linux AppStream EUS (v. 8.2)Fixed RHSA-2021:5016, RHSA-2021:5047
Red Hat Enterprise Linux AppStream EUS (v.8.4)Fixed RHSA-2021:5015, RHSA-2021:5048
Red Hat Enterprise Linux Client (v. 7)Fixed RHSA-2021:5014, RHSA-2021:5046
Red Hat Enterprise Linux Client Optional (v. 7)Fixed RHSA-2021:5014
Red Hat Enterprise Linux Server (v. 7)Fixed RHSA-2021:5014
Red Hat Enterprise Linux Server Optional (v. 7)Fixed RHSA-2021:5014, RHSA-2021:5046
Red Hat Enterprise Linux Workstation (v. 7)Fixed RHSA-2021:5014, RHSA-2021:5046
Red Hat Enterprise Linux Workstation Optional (v. 7)Fixed RHSA-2021:5014

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-4129
  2. 2026-10-03 Alias added: GHSA-v25r-h4v7-62rr

References

Exploit 1

Advisory 3

  • 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