VDB
CVE-2026-109778
CVE-2026-109778
PUBLISHED
CVSS 8.8 HIGH
Privilege escalation in the WebExtensions component
Reported by mozilla · Published October 13, 2026
Privilege escalation in the WebExtensions component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
Fixed versions
Upgrade to a fixed version or later. Language registries are listed first, then Linux distributions, then vendor products.
| Package | Ecosystem | Fixed in |
|---|---|---|
| thunderbird-debugsource | errata.rockylinux.org | 0:153.5.0-1.el9_8.x86_64, 0:153.5.0-1.el9_8.s390x, 0:153.5.0-1.el9_8.ppc64le, 0:153.5.0-1.el9_8.aarch64 |
| thunderbird | errata.rockylinux.org | 0:153.5.0-1.el9_8.x86_64, 0:153.5.0-1.el9_8.src, 0:153.5.0-1.el9_8.s390x, 0:153.5.0-1.el9_8.ppc64le, 0:153.5.0-1.el9_8.aarch64 |
| thunderbird-debuginfo | errata.rockylinux.org | 0:153.5.0-1.el9_8.x86_64, 0:153.5.0-1.el9_8.s390x, 0:153.5.0-1.el9_8.ppc64le, 0:153.5.0-1.el9_8.aarch64 |
| firefox | Amazon Linux | 153.5.0-1.amzn2023.0.1 |
| thunderbird | Amazon Linux | 153.5.1-1.amzn2.0.1 |
| firefox-esr-140 | Chainguard | 140.17.0-r2 |
Risk scores
CVSS 3.1
8.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Affected products
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | 153.5, 158 |
| Mozilla | Thunderbird | 153.5, 158 |
| Mozilla | Thunderbird | 153.5, 158 |
| amazon:2023 | firefox | 0 |
| amazon:2 | thunderbird | 0 |
| chainguard | firefox-esr-140 | 0 |
| Mozilla | Firefox | 158, 153.5 |
Timeline
- Oct 13, 2026 CVE Published
- Oct 14, 2026 EPSS Score (6 in total, the first dated here)
- Oct 14, 2026 CVE Updated
- Nov 4, 2026 Distribution Patch
- Nov 4, 2026 Security Advisory
Query this with the API
The same record, from the CLI:
vulnetix vdb vuln CVE-2026-109778
vulnetix vdb fixes CVE-2026-109778Or with curl, using the org id and key from your account page:
curl -s -H "Authorization: ApiKey ${VULNETIX_ORG_ID}:${VULNETIX_API_KEY}" \
"https://api.vdb.vulnetix.com/v2/vuln/CVE-2026-109778/fixes/registry"The Community plan is free and allows 50 queries a day. Get a free API key · API quickstart