External risk intelligence

Firefox Graphics ImageLib Integer Overflow

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-16402

This vulnerability exists within a client-side graphics component of the Firefox web browser. It is not a network-facing service, API, or edge gateway. Exploitation requires a user to perform a client-side action, such as viewing malicious content within the browser, rather than targeting an internet-facing server or appliance.

Integer Overflow

Mozilla Firefox

before 153.0.0before 153.0

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

This critical vulnerability resides in a graphics component of the Firefox web browser, specifically an integer overflow in how images are processed. While it requires user interaction to exploit, such as visiting a malicious website, it could allow an attacker to compromise the browser with high impact, potentially affecting confidentiality, integrity, and availability. The main concern at this stage is confirming relevance and exposure within our environment.

Image processing flaw in Firefox browser.
Affects user interactions; potential for high impact.
Confirm relevance and exposure.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by tricking a user into visiting a malicious webpage. This would allow them to trigger an integer overflow in the Graphics: ImageLib component, which could lead to a complete compromise of the user's system.

No special access required.
Triggered by viewing malicious content.
Leads to complete system compromise.

Live Threat

Current exploitation, exposure, and threat context

An integer overflow in the Graphics: ImageLib component could allow an attacker to execute arbitrary code when a user loads a specially crafted image. This could lead to the compromise of the user's system.

User-loaded images.
Specially crafted image files.
Arbitrary code execution.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in the Graphics: ImageLib component affects the Firefox web browser, specifically impacting client-side rendering of images. Responsibility for addressing this typically falls to teams managing end-user computing environments and browser security, such as IT operations or desktop support, in coordination with security teams responsible for monitoring and managing external threats. The first practical step is to identify all instances of the affected browser version, assess exposure based on user activity and reachability, and then plan for remediation, likely involving browser updates or policy enforcement to mitigate risk.

End-user computing and browser security teams.
Confirm affected browser versions and user exposure.
Plan controlled updates or policy enforcement.

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 Firefox Graphics: ImageLib component?

ImageLib is a core internal library within the Firefox web browser responsible for decoding, rendering, and processing various image formats. When you view a webpage, this component handles the task of converting image data into the visual graphics displayed on your screen.

What does CWE-190 mean for CVE-2026-16402?

CWE-190 refers to an integer overflow, a weakness where a calculation exceeds the memory capacity allocated to store it. In the context of this CVE, the ImageLib component fails to safely handle large or specially crafted image data, which can cause the software to behave unexpectedly, potentially allowing an attacker to execute malicious code on the system.

How is this integer overflow triggered?

The vulnerability is triggered when the Firefox browser attempts to process a specially crafted image file. An attacker initiates this by tricking a user into navigating to a malicious website or viewing harmful content. Simply having the browser installed does not trigger the bug; the browser must actively parse the malicious image data.

Is my system at risk if I use Firefox?

Halo Surface Signal indicates this is a client-side issue rather than a network-facing service or server vulnerability. Because it resides in the browser's graphics processing, it primarily impacts end-user devices. The risk is focused on users who interact with untrusted content, making it less relevant to internal infrastructure that does not perform web browsing.

What should I do to secure my environment?

The first step is to identify all systems running vulnerable versions of Firefox. Coordinate with IT or desktop management teams to prioritize updates to Firefox 153 or later, which contains the fix for this issue. Verify that automatic update policies are active to ensure users receive this patch promptly and minimize the window of potential risk.

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.