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HIGH

CVE-2026-109778

Privilege escalation in the WebExtensions component

CVSS v3

8.8

HIGH

EPSS Score

—

exploit probability

CISA KEV

No

known exploited

Exploitation

none

SSVC status

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Affected and fixed versions

Neither OSV.dev nor the vendor advisories we read list affected versions for CVE-2026-109778 yet.

Full record on NVD

Description

Privilege escalation in the WebExtensions component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Published
2026-10-13
Last Modified
2026-10-14

Frequently asked questions

What is CVE-2026-109778?

Privilege escalation in the WebExtensions component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

Is CVE-2026-109778 actively exploited?

Active exploitation of CVE-2026-109778 has not been confirmed.

What is the CVSS score for CVE-2026-109778?

CVE-2026-109778 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

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