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TI-2026-57842 Aliases CVE-2026-84121GHSA-5g9x-cffv-ccj8

Use after free in Mozilla Firefox

Priority MEDIUM 43CWE-416Published · 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: 14 fixed, 3 without a fix

Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA and Red Hat. Impact type from CWE-416 and the CVSS impact.

Summary

Sandbox escape due to use-after-free in the DOM: Security component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00319 25th percentileScored 2026-11-07
Fix Partial Firefox (Mozilla): 115.40, 140.15, 153.2 +1Thunderbird (Mozilla): 140.15, 153.2, 155Red Hat: 21 advisoriesRed Hat: 14 fixed, 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
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
MozillaFirefox—115.40, 140.15, 153.2, 155Patch availableCNA
MozillaThunderbird—140.15, 153.2, 155Patch availableCNA
  • Firefox VendorMozilla Affected — Fixed in 115.40, 140.15, 153.2, 155 Patch available CNA
  • Thunderbird VendorMozilla Affected — Fixed in 140.15, 153.2, 155 Patch available CNA

CPE configurations NVD · 2

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*before 115.40.0; 116.0 to before 140.15.0; 141.0.0 to before 153.2.0; 154.0.0 to before 155.0.0VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*before 140.15.0; 141.0 to before 153.2.0; 154.0 to before 155.0VulnerableMozilla
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions before 115.40.0; 116.0 to before 140.15.0; 141.0.0 to before 153.2.0; 154.0.0 to before 155.0.0 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions before 140.15.0; 141.0 to before 153.2.0; 154.0 to before 155.0 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Firefox (Mozilla) Fixed in 115.40, 140.15, 153.2, 155
  • Fix · CNA Thunderbird (Mozilla) Fixed in 140.15, 153.2, 155

Red Hat 21 advisories

  • RHSA-2026:82122 Released 2026-10-13 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.4) thunderbird-140.16.0-1.el8_4
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) thunderbird-140.16.0-1.el8_4
  • RHSA-2026:81912 Released 2026-10-13 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v.8.8) thunderbird-140.16.0-1.el8_8
    • Red Hat Enterprise Linux AppStream TUS (v.8.8) thunderbird-140.16.0-1.el8_8
  • RHSA-2026:81913 Released 2026-10-13 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.6) thunderbird-140.16.0-1.el8_6
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) thunderbird-140.16.0-1.el8_6
Show 18 more Red Hat advisories
  • RHSA-2026:80503 Released 2026-10-12 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v.9.6) thunderbird-140.15.0-1.el9_6
  • RHSA-2026:77632 Released 2026-10-08 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.2) thunderbird-140.15.0-1.el9_2
  • RHSA-2026:77627 Released 2026-10-08 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.4) thunderbird-140.15.0-1.el9_4
  • RHSA-2026:77631 Released 2026-10-08 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 10.0) thunderbird-140.15.0-1.el10_0
  • RHSA-2026:77610 Released 2026-10-07 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v. 10.0) firefox-140.15.0-1.el10_0
  • RHSA-2026:76895 Released 2026-10-06 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v.9.6) firefox-140.15.0-1.el9_6, firefox-x11-140.15.0-1.el9_6
  • RHSA-2026:76894 Released 2026-10-06 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.4) firefox-140.15.0-1.el8_4
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) firefox-140.15.0-1.el8_4
  • RHSA-2026:76742 Released 2026-10-06 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.2) firefox-140.15.0-1.el9_2, firefox-x11-140.15.0-1.el9_2
  • RHSA-2026:76740 Released 2026-10-06 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.4) firefox-140.15.0-1.el9_4, firefox-x11-140.15.0-1.el9_4
  • RHSA-2026:76741 Released 2026-10-06 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux Server (v. 7 ELS) firefox-140.15.0-1.el7_9
  • RHSA-2026:76745 Released 2026-10-06 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.6) firefox-140.15.0-1.el8_6
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) firefox-140.15.0-1.el8_6
  • RHSA-2026:76746 Released 2026-10-06 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream E4S (v.8.8) firefox-140.15.0-1.el8_8
    • Red Hat Enterprise Linux AppStream TUS (v.8.8) firefox-140.15.0-1.el8_8
  • RHSA-2026:73971 Released 2026-09-30 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 8) thunderbird-140.16.0-1.el8_10
  • RHSA-2026:73130 Released 2026-09-29 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 10) thunderbird-140.16.0-1.el10_2
  • RHSA-2026:70642 Released 2026-09-24 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 9) thunderbird-140.16.0-1.el9_8
  • RHSA-2026:68549 Released 2026-09-17 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream (v. 8) firefox-140.15.0-1.el8_10
  • RHSA-2026:67133 Released 2026-09-14 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream (v. 9) firefox-140.15.0-1.el9_8, firefox-x11-140.15.0-1.el9_8
  • RHSA-2026:67129 Released 2026-09-14 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream (v. 10) firefox-140.15.0-1.el10_2

Vendor assessments

Red Hat

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

ProductStatusPlan or fix
Red Hat Enterprise Linux 10AffectedNo fix yet
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 7AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux AppStream (v. 10)Fixed RHSA-2026:67129, RHSA-2026:73130
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2026:68549, RHSA-2026:73971
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2026:67133, RHSA-2026:70642
Red Hat Enterprise Linux AppStream AUS (v.8.4)Fixed RHSA-2026:76894, RHSA-2026:82122
Red Hat Enterprise Linux AppStream AUS (v.8.6)Fixed RHSA-2026:76745, RHSA-2026:81913
Red Hat Enterprise Linux AppStream E4S (v.8.8)Fixed RHSA-2026:76746, RHSA-2026:81912
Red Hat Enterprise Linux AppStream E4S (v.9.2)Fixed RHSA-2026:76742, RHSA-2026:77632
Red Hat Enterprise Linux AppStream E4S (v.9.4)Fixed RHSA-2026:76740, RHSA-2026:77627
Red Hat Enterprise Linux AppStream EUS (v. 10.0)Fixed RHSA-2026:77610, RHSA-2026:77631
Red Hat Enterprise Linux AppStream EUS (v.9.6)Fixed RHSA-2026:76895, RHSA-2026:80503
Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)Fixed RHSA-2026:76894, RHSA-2026:82122
Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)Fixed RHSA-2026:76745, RHSA-2026:81913
Red Hat Enterprise Linux AppStream TUS (v.8.8)Fixed RHSA-2026:76746, RHSA-2026:81912
Red Hat Enterprise Linux Server (v. 7 ELS)Fixed RHSA-2026:76741

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-84121
  2. 2026-10-03 Alias added: GHSA-5g9x-cffv-ccj8
  3. 2026-10-06 Fix available: RHSA-2026:76741 · Red Hat
  4. 2026-10-06 Fix available: RHSA-2026:76740 · Red Hat
  5. 2026-10-06 Fix available: RHSA-2026:76746 · Red Hat
  6. 2026-10-06 Fix available: RHSA-2026:76742 · Red Hat
  7. 2026-10-06 Fix available: Red Hat Enterprise Linux AppStream E4S (v.8.8), Red Hat Enterprise Linux AppStream E4S (v.9.2), Red Hat Enterprise Linux AppStream E4S (v.9.4) +2 · Red Hat
  8. 2026-10-07 Fix available: RHSA-2026:76745 · Red Hat
  9. 2026-10-07 Fix available: RHSA-2026:76894 · Red Hat
  10. 2026-10-07 Fix available: RHSA-2026:76895 · Red Hat
  11. 2026-10-07 Fix available: Red Hat Enterprise Linux AppStream AUS (v.8.4), Red Hat Enterprise Linux AppStream AUS (v.8.6), Red Hat Enterprise Linux AppStream EUS (v.9.6) +2 · Red Hat
  12. 2026-10-07 Fix available: RHSA-2026:77610 · Red Hat
  13. 2026-10-07 Fix available: Red Hat Enterprise Linux AppStream EUS (v. 10.0) · Red Hat
  14. 2026-10-08 Affected versions changed · Red Hat
  15. 2026-10-09 Fix available: RHSA-2026:77631 · Red Hat
  16. 2026-10-09 Fix available: RHSA-2026:77627 · Red Hat
  17. 2026-10-09 Fix available: RHSA-2026:77632 · Red Hat
  18. 2026-10-12 Fix available: RHSA-2026:80503 · Red Hat
  19. 2026-10-12 Affected versions changed · Red Hat
  20. 2026-10-13 Fix available: RHSA-2026:81912 · Red Hat
  21. 2026-10-13 Fix available: RHSA-2026:81913 · Red Hat
  22. 2026-10-13 Affected versions changed · Red Hat
  23. 2026-10-14 Fix available: RHSA-2026:82122 · Red Hat

References

Advisory 7

Other 1

  • 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