CVE-2026-109778
Privilege escalation in the WebExtensions component
At a glance
- Severity
- HIGH 8.8
- EPSS
- EPSS 0.28 % · percentile 20 (2026-10-27)
- State
- PUBLISHED
- Published
- Updated
- Assigner
- mozilla
- NVD status
- Deferred
Description
Privilege escalation in the WebExtensions component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | HIGH 8.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H | CISA-ADP |
| CVSS 3.1 | HIGH 8.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H | NVD · 134c704f-9b21-4f2e-91b3-4a467353bcc0 (Secondary) |
Weaknesses (CWE)
European references
- ENISA EUVD · EUVD-2026-98538
- GCVE · GCVE-0-2026-109778
CERT-FR advisories
- CERTFR-2026-AVI-1305 — Multiples vulnérabilités dans les produits Mozilla · cert.ssi.gouv.fr
Affected products
| Product | Versions |
|---|---|
| Mozilla · Firefox | unaffected 153.5 ≤ 153.* ; unaffected 158 ≤ * |
| Mozilla · Thunderbird | unaffected 153.5 ≤ 153.* ; unaffected 158 ≤ * |
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2070547
- https://www.mozilla.org/security/advisories/mfsa2026-106/
- https://www.mozilla.org/security/advisories/mfsa2026-108/
- https://www.mozilla.org/security/advisories/mfsa2026-109/
- https://www.mozilla.org/security/advisories/mfsa2026-110/
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |