CVE-2025-6436Network attack vector

Arbitrary code execution via memory corruption

Published Jun 24, 2025 · Updated Apr 13, 2026

Memory corruption in Mozilla Firefox and Thunderbird 139 allows attackers to execute arbitrary code via unspecified vectors. Mozilla groups five memory-safety defects under this identifier, but the individual code loci and unsafe operations are not publicly disclosed. Firefox is exposed in browser contexts; Thunderbird generally blocks email-based exploitation because scripting is disabled when reading mail.

CVSS severity8.1
High
EPSS probability3.51%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Mozilla Firefox and Thunderbird 139 allows attackers to execute arbitrary code via unspecified vectors. Mozilla groups five memory-safety defects under this identifier, but the individual code loci and unsafe operations are not publicly disclosed. Firefox is exposed in browser contexts; Thunderbird generally blocks email-based exploitation because scripting is disabled when reading mail.

The record

CVE
CVE-2025-6436
Published
Jun 24, 2025
Updated
Apr 13, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-119
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 24, 2025CVE publishedPublication date reported by the CVE source.
  2. Apr 13, 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

8.1UbuntuCVSS:3.1/AV:N/AC:H/PR:N/UI:N/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.

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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-119Improper Restriction of Operations within the Bounds of a Memory Buffer

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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