CVE-2026-6764Network attack vector

Unauthenticated data modification and service interruption

Published Apr 21, 2026 · Updated Apr 21, 2026

An out-of-bounds flaw in Firefox and Thunderbird allows remote attackers to modify data and interrupt service through network content. Mozilla identifies the locus only as DOM: Device Interfaces, while the permission-restricted bug leaves the incorrect operation on untrusted input publicly undisclosed. Exploitation requires no authentication or additional user interaction; Thunderbird disables scripting while reading email, limiting exposure there to browser or browser-like contexts.

CVSS severity6.5
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

An out-of-bounds flaw in Firefox and Thunderbird allows remote attackers to modify data and interrupt service through network content. Mozilla identifies the locus only as DOM: Device Interfaces, while the permission-restricted bug leaves the incorrect operation on untrusted input publicly undisclosed. Exploitation requires no authentication or additional user interaction; Thunderbird disables scripting while reading email, limiting exposure there to browser or browser-like contexts.

The record

CVE
CVE-2026-6764
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-119, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 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

6.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

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-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1203Exploitation for Client Execution

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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