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TI-2026-71664 Aliases CVE-2026-109739GHSA-xc46-c8p5-77m7

Privilege escalation in Mozilla WebExtensions component

Priority MEDIUM 40CWE-269Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Privilege escalation
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA. Impact type from CWE-269.

Summary

Mozilla Firefox and Thunderbird are affected, and both are fixed in version 158. Improper privilege management in the WebExtensions component lets an attacker with low privileges gain higher privileges over the network. CVSS 3.1 rates it HIGH (8.8), with total impact on confidentiality, integrity and availability. CISA has not added it to KEV, and the references contain no exploit link.

Written with Claude Haiku 5.5 from the sources below · 2026-10-31

Description from the CNA

Privilege escalation in the WebExtensions component. This vulnerability was fixed in Firefox 158 and Thunderbird 158.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00369 30th percentileScored 2026-11-07
Fix Fixed Firefox (Mozilla): 158Thunderbird (Mozilla): 158

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—158Patch availableCNA
MozillaThunderbird—158Patch availableCNA
  • Firefox VendorMozilla Affected — Fixed in 158 Patch available CNA
  • Thunderbird VendorMozilla Affected — Fixed in 158 Patch available CNA

CPE names Threatist (inferred) · 2

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*——Mozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*——Mozilla
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions — — ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions — — ·Mozilla

Remediation

Update Firefox to version 158 and Thunderbird to version 158.

Written with Claude Haiku 5.5 from the sources below · 2026-10-31

  • Fix · CNA Firefox (Mozilla) Fixed in 158
  • Fix · CNA Thunderbird (Mozilla) Fixed in 158

Vendor assessments

Red Hat

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

Not affected: 5 products
  • Red Hat Enterprise Linux 10
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9

Timeline

  1. 2026-10-13 Threatist record created from CVE-2026-109739
  2. 2026-10-13 Alias added: GHSA-xc46-c8p5-77m7
  3. 2026-10-13 Fix available: Mozilla/Thunderbird@158 · CNA
  4. 2026-10-13 1 new reference · CNA
  5. 2026-10-14 CISA SSVC decision points changed
  6. 2026-10-14 Weakness changed · CISA ADP
  7. 2026-10-14 CISA SSVC decision points changed
  8. 2026-10-14 CVSS score added · CISA ADP
  9. 2026-10-16 Priority changed: LOW → MEDIUM
  10. 2026-10-31 Affected versions changed · Red Hat
  11. 2026-10-31 CVSS score added · Red Hat

References

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 4204 →

Sources

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