CVE-2026-84128

Privilege escalation

Published Sep 1, 2026 · Updated Sep 2, 2026

Improper access control in Mozilla Firefox and Thunderbird before 155 allows attackers to escalate privileges through WebDriver BiDi. Mozilla has not disclosed the affected WebDriver BiDi locus or the incorrect authorization operation performed on untrusted input. Reaching the flaw requires interaction with WebDriver BiDi; published material does not identify the privileges gained or whether ordinary browsing or email content can trigger it.

CVSS severity4.1
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in Mozilla Firefox and Thunderbird before 155 allows attackers to escalate privileges through WebDriver BiDi. Mozilla has not disclosed the affected WebDriver BiDi locus or the incorrect authorization operation performed on untrusted input. Reaching the flaw requires interaction with WebDriver BiDi; published material does not identify the privileges gained or whether ordinary browsing or email content can trigger it.

The record

CVE
CVE-2026-84128
Published
Sep 1, 2026
Updated
Sep 2, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1068
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Sep 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.1Amazon LinuxCVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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