CVE-2026-84120Network attack vector

Code execution via expired pointer dereference

Published Sep 1, 2026 · Updated Sep 1, 2026

Expired pointer dereference in Mozilla Firefox and Thunderbird allows remote attackers to execute code via unspecified Audio/Video input. The Audio/Video component dereferences a pointer after its referenced memory has been freed, but Mozilla has not disclosed the affected function or trigger. Exploitation requires user interaction; Thunderbird disables scripting while reading mail, limiting exposure to browser or browser-like contexts.

CVSS severity5.4
Medium
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Expired pointer dereference in Mozilla Firefox and Thunderbird allows remote attackers to execute code via unspecified Audio/Video input. The Audio/Video component dereferences a pointer after its referenced memory has been freed, but Mozilla has not disclosed the affected function or trigger. Exploitation requires user interaction; Thunderbird disables scripting while reading mail, limiting exposure to browser or browser-like contexts.

The record

CVE
CVE-2026-84120
Published
Sep 1, 2026
Updated
Sep 1, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-825, T1203
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

5.4cve.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
8.8Red HatCVSS:3.1/AV:N/AC:L/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-825Expired Pointer Dereference
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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