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TI-2026-05027 Aliases CVE-2026-5734GHSA-qf82-86x2-7q23

Memory safety bugs fixed in Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2

Priority MEDIUM 43CWE-120Published · 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: 17 fixed, 3 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-120 and the CVSS impact.

Summary

Memory safety bugs present in Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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 was fixed in Firefox 149.0.2, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00342 27th percentileScored 2026-11-07
Fix Partial Firefox (Mozilla): 140.9.1, 149.0.2Thunderbird (Mozilla): 140.9.1, 149.0.2Red Hat: 24 advisoriesRed Hat: 17 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—140.9.1, 149.0.2Patch availableCNA
MozillaThunderbird—140.9.1, 149.0.2Patch availableCNA
  • Firefox VendorMozilla Affected — Fixed in 140.9.1, 149.0.2 Patch available CNA
  • Thunderbird VendorMozilla Affected — Fixed in 140.9.1, 149.0.2 Patch available CNA

CPE configurations NVD · 4

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*before 140.9.1VulnerableMozilla
cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*before 149.0.2VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*before 140.9.1VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*before 149.0.2VulnerableMozilla
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:* Versions before 140.9.1 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:* Versions before 149.0.2 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:* Versions before 140.9.1 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:* Versions before 149.0.2 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Firefox (Mozilla) Fixed in 140.9.1, 149.0.2
  • Fix · CNA Thunderbird (Mozilla) Fixed in 140.9.1, 149.0.2

Red Hat 24 advisories

  • RHSA-2026:15889 Released 2026-05-11 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.6) thunderbird-140.9.1-1.el8_6
    • Red Hat Enterprise Linux AppStream E4S (v.8.6) thunderbird-140.9.1-1.el8_6
    • Red Hat Enterprise Linux AppStream TUS (v.8.6) thunderbird-140.9.1-1.el8_6
  • RHSA-2026:14303 Released 2026-05-06 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.4) thunderbird-140.9.1-1.el8_4
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) thunderbird-140.9.1-1.el8_4
  • RHSA-2026:14223 Released 2026-05-06 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v.8.8) thunderbird-140.9.1-1.el8_8
    • Red Hat Enterprise Linux AppStream TUS (v.8.8) thunderbird-140.9.1-1.el8_8
Show 21 more Red Hat advisories
  • RHSA-2026:13977 Released 2026-05-06 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux Server (v. 7 ELS) firefox-140.9.1-2.el7_9
  • RHSA-2026:13922 Released 2026-05-06 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.2) firefox-140.9.1-1.el9_2, firefox-x11-140.9.1-1.el9_2
  • RHSA-2026:13683 Released 2026-05-05 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.6) firefox-140.9.1-1.el8_6
    • Red Hat Enterprise Linux AppStream E4S (v.8.6) firefox-140.9.1-1.el8_6
    • Red Hat Enterprise Linux AppStream TUS (v.8.6) firefox-140.9.1-1.el8_6
  • RHSA-2026:13682 Released 2026-05-05 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream E4S (v.8.8) firefox-140.9.1-1.el8_8
    • Red Hat Enterprise Linux AppStream TUS (v.8.8) firefox-140.9.1-1.el8_8
  • RHSA-2026:13665 Released 2026-05-05 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v. 10.0) firefox-140.9.1-1.el10_0
  • RHSA-2026:13600 Released 2026-05-05 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.4) firefox-140.9.1-1.el8_4
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) firefox-140.9.1-1.el8_4
  • RHSA-2026:13583 Released 2026-05-05 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v.9.6) firefox-140.9.1-1.el9_6, firefox-x11-140.9.1-1.el9_6
  • RHSA-2026:13582 Released 2026-05-05 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v.9.4) firefox-140.9.1-1.el9_4, firefox-x11-140.9.1-1.el9_4
  • RHSA-2026:13596 Released 2026-05-05 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.0) firefox-140.9.1-1.el9_0
  • RHSA-2026:13533 Released 2026-05-04 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v.9.4) thunderbird-140.9.1-1.el9_4
  • RHSA-2026:13412 Released 2026-05-04 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.2) thunderbird-140.9.1-1.el9_2
  • RHSA-2026:13342 Released 2026-05-04 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v.9.6) thunderbird-140.9.1-1.el9_6
  • RHSA-2026:12264 Released 2026-04-30 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.0) thunderbird-140.9.1-1.el9_0
  • RHSA-2026:11813 Released 2026-04-29 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 10.0) thunderbird-140.9.1-1.el10_0
  • RHSA-2026:11805 Released 2026-04-29 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream AUS (v. 8.2) firefox-140.9.1-1.el8_2
  • RHSA-2026:9638 Released 2026-04-22 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 10) thunderbird-140.9.1-1.el10_1
  • RHSA-2026:9345 Released 2026-04-21 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 8) thunderbird-140.9.1-1.el8_10
  • RHSA-2026:8459 Released 2026-04-16 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 9) thunderbird-140.9.1-1.el9_7
  • RHSA-2026:8052 Released 2026-04-14 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream (v. 8) firefox-140.9.1-1.el8_10
  • RHSA-2026:7671 Released 2026-04-13 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream (v. 9) firefox-140.9.1-1.el9_7, firefox-x11-140.9.1-1.el9_7
  • RHSA-2026:7672 Released 2026-04-13 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream (v. 10) firefox-140.9.1-1.el10_1

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-2026:7672, RHSA-2026:9638
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2026:8052, RHSA-2026:9345
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2026:7671, RHSA-2026:8459
Red Hat Enterprise Linux AppStream AUS (v. 8.2)Fixed RHSA-2026:11805
Red Hat Enterprise Linux AppStream AUS (v.8.4)Fixed RHSA-2026:13600, RHSA-2026:14303
Red Hat Enterprise Linux AppStream AUS (v.8.6)Fixed RHSA-2026:13683, RHSA-2026:15889
Red Hat Enterprise Linux AppStream E4S (v.8.6)Fixed RHSA-2026:13683, RHSA-2026:15889
Red Hat Enterprise Linux AppStream E4S (v.8.8)Fixed RHSA-2026:13682, RHSA-2026:14223
Red Hat Enterprise Linux AppStream E4S (v.9.0)Fixed RHSA-2026:12264, RHSA-2026:13596
Red Hat Enterprise Linux AppStream E4S (v.9.2)Fixed RHSA-2026:13412, RHSA-2026:13922
Red Hat Enterprise Linux AppStream EUS (v. 10.0)Fixed RHSA-2026:11813, RHSA-2026:13665
Red Hat Enterprise Linux AppStream EUS (v.9.4)Fixed RHSA-2026:13533, RHSA-2026:13582
Red Hat Enterprise Linux AppStream EUS (v.9.6)Fixed RHSA-2026:13342, RHSA-2026:13583
Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)Fixed RHSA-2026:13600, RHSA-2026:14303
Red Hat Enterprise Linux AppStream TUS (v.8.6)Fixed RHSA-2026:13683, RHSA-2026:15889
Red Hat Enterprise Linux AppStream TUS (v.8.8)Fixed RHSA-2026:13682, RHSA-2026:14223
Red Hat Enterprise Linux Server (v. 7 ELS)Fixed RHSA-2026:13977

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-5734
  2. 2026-10-03 Alias added: GHSA-qf82-86x2-7q23

References

Advisory 2

Other 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