High 8.8Published Sep 1, 2026

CVE-2026-84128Privilege escalation in the WebDriver BiDi component

Updated under an hour ago (2026-10-19 06:25 UTC)

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It affects Mozilla Firefox and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

Privilege escalation in the WebDriver BiDi component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.

CVSS: 8.8 HIGH (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-284
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: mozilla
NVD analysis: Analyzed
Record last updated: Sep 2, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Mozilla Firefox mozilla:firefox (from the name)	from 155 not affected	CNA record
Mozilla Thunderbird mozilla:thunderbird (from the name)	from 155 not affected	CNA record
mozilla firefox mozilla:firefox	before 155.0.0	NVD
mozilla thunderbird mozilla:thunderbird	before 155.0	NVD

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2044280permissions-required
https://www.mozilla.org/security/advisories/mfsa2026-82/vendor-advisory
https://www.mozilla.org/security/advisories/mfsa2026-86/vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.