CVE-2026-6759Network attack vector

Application crash via undisclosed Cocoa use-after-free

Published Apr 21, 2026 · Updated Apr 21, 2026

Use-after-free in Mozilla Firefox and Thunderbird before 150, including ESR 140 before 140.10, allows remote attackers to crash the application. Mozilla has not published which Cocoa widget object is freed prematurely or which later operation dereferences it; the linked bug is access-restricted. The flaw is reachable without authentication or user interaction, and the published impact is limited to application unavailability.

CVSS severity7.5
High
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Mozilla Firefox and Thunderbird before 150, including ESR 140 before 140.10, allows remote attackers to crash the application. Mozilla has not published which Cocoa widget object is freed prematurely or which later operation dereferences it; the linked bug is access-restricted. The flaw is reachable without authentication or user interaction, and the published impact is limited to application unavailability.

The record

CVE
CVE-2026-6759
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416, T1499
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

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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.

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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-416Use After Free
T1499Endpoint Denial of Service

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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