CVE-2026-74934Network attack vector

CanvasWebGL site isolation bypass

Published Aug 18, 2026 · Updated Aug 18, 2026

Site isolation bypass in Mozilla Firefox and Thunderbird allows remote attackers to cross CanvasWebGL security boundaries via crafted web content. Mozilla has not published the defective CanvasWebGL operation or explained how untrusted graphics input defeats site isolation. Exploitation requires user interaction with web content; Thunderbird mail reading disables scripting, limiting exposure to browser-like contexts.

CVSS severity7.5
High
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Site isolation bypass in Mozilla Firefox and Thunderbird allows remote attackers to cross CanvasWebGL security boundaries via crafted web content. Mozilla has not published the defective CanvasWebGL operation or explained how untrusted graphics input defeats site isolation. Exploitation requires user interaction with web content; Thunderbird mail reading disables scripting, limiting exposure to browser-like contexts.

The record

CVE
CVE-2026-74934
Published
Aug 18, 2026
Updated
Aug 18, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-284, CWE-346, CWE-200
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 18, 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

7.5CISA-ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

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 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-284Improper Access Control
CWE-346Origin Validation Error
CWE-200Exposure of Sensitive Information to an Unauthorized Actor

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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