CVE-2026-84126Network attack vector

Data disclosure via incorrect Grid boundaries

Published Sep 1, 2026 · Updated Sep 1, 2026

Incorrect boundary conditions in Mozilla Firefox and Thunderbird before 155 allow remote attackers to disclose data through crafted web content. The Layout: Grid component applies incorrect boundary conditions, but Mozilla has not disclosed the affected routine or the precise operation performed on attacker-controlled layout data. Exploitation requires user interaction with browser content; disabled scripting while reading Thunderbird email limits ordinary message-based exposure.

CVSS severity4.3
Medium
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect boundary conditions in Mozilla Firefox and Thunderbird before 155 allow remote attackers to disclose data through crafted web content. The Layout: Grid component applies incorrect boundary conditions, but Mozilla has not disclosed the affected routine or the precise operation performed on attacker-controlled layout data. Exploitation requires user interaction with browser content; disabled scripting while reading Thunderbird email limits ordinary message-based exposure.

The record

CVE
CVE-2026-84126
Published
Sep 1, 2026
Updated
Sep 1, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-120
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 1, 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 vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3CISA ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

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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