External risk intelligence

Use-After-Free in Mozilla GMP Component

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2025-14326

This vulnerability exists in the Audio/Video: GMP component of web browsers and email clients. While these applications are used to access the internet, this specific component processes media content locally on the end-user's device. It does not represent an internet-facing service, gateway, or management interface that is exposed to public network traffic.

Use After Free

Mozilla Firefox

before 146.0

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A critical vulnerability has been identified in the audio and video component of widely used Mozilla products, including Firefox and Thunderbird. This flaw, if exploited, could allow an attacker to remotely compromise systems without any user interaction, potentially leading to significant data breaches or service disruptions. The primary concern is to confirm if our environment is affected by this specific component and to what extent.

Flaw in audio/video processing.
Critical remote compromise risk.
Confirm relevance and exposure.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending specially crafted media content to a user, which would be processed by the Audio/Video: GMP component within Firefox or Thunderbird. Successful exploitation could lead to an attacker gaining control over the user's system.

No special access required.
Triggered by viewing malicious media.
Leads to significant system compromise.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability in the Audio/Video: GMP component could impact the integrity and availability of the affected applications when processing media content.

Application integrity and availability could be affected.
Vulnerable processing of media content could lead to issues.
Unspecified service disruption or data corruption may occur.

Operational Fix

Recommended remediation, mitigation, and detection steps

The Audio/Video: GMP component within Firefox and Thunderbird is the focus of this critical vulnerability. Responsibility for addressing this likely falls to the platform or application teams managing these user-facing tools. The immediate first step is to inventory all instances of Firefox and Thunderbird, determine their reachability, and identify the accountable owners before planning a coordinated remediation effort.

Platform/application teams own remediation.
Verify all Firefox and Thunderbird instances.
Plan updates during maintenance windows.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the GMP component in Firefox and Thunderbird?

The GMP (Gecko Media Plugin) component is a framework within Mozilla Firefox and Thunderbird that handles the decoding and playback of audio and video content. It acts as a bridge between the browser or email client and specialized plugins needed to render different media formats when you visit websites or open messages containing multimedia.

What does a use-after-free vulnerability mean in CVE-2025-14326?

This is a memory management error categorized as CWE-416. It occurs when a program continues to use a pointer to a memory address after that memory has been cleared or deallocated. In this specific case, the flaw in the media plugin logic could allow an attacker to manipulate that freed memory space to execute unauthorized commands or cause the application to crash.

How is this vulnerability triggered?

The flaw is triggered when the browser or email client processes specially crafted media content. An attacker must deliver this malicious file to the user, who then views or plays the content. Simply having the software installed is not enough; the specific, harmful media data must be loaded and processed by the affected plugin component to initiate the memory error.

Is this CVE considered internet-facing according to Halo Surface Signal?

No. While these applications browse the internet, Halo Surface Signal notes that the vulnerable GMP component processes media content locally on the user's device. It is not an internet-facing service, gateway, or management interface that listens for public network traffic, meaning it does not fit the profile of a typical externally exposed network service.

What steps should I take if I use these applications?

Your first step is to inventory all instances of Firefox and Thunderbird within your environment to identify which systems are running versions prior to 146. Once identified, ensure your teams coordinate to update these applications to version 146 or later, as these releases contain the necessary fixes provided by Mozilla to resolve the use-after-free defect.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.