External risk intelligence

Firefox and Thunderbird Web Audio Component Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-2773

The vulnerability exists within the Web Audio component of client-side software (Firefox and Thunderbird). While these applications retrieve content from the internet, the component itself is a client-side library, not a public-facing network service, appliance, or gateway, and is not designed to be reachable as an externally exposed attack surface.

Memory Corruption

Mozilla Firefox

before 115.33.0before 148.0128.0 to before 140.8.0before 140.8.0

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 Web Audio component of Firefox and Thunderbird. This issue presents a significant risk due to its exploitable nature over the network without requiring user interaction or authentication, potentially allowing for severe data compromise and disruption. The main concern is confirming relevance and exposure given the nature of the affected component.

Incorrect boundary conditions in Web Audio.
Critical risk for data compromise and disruption.
Confirm relevance and exposure of affected applications.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by tricking a user into visiting a malicious website. This would involve interacting with the Web Audio component, which, if improperly handled, could allow the attacker to achieve high confidentiality, integrity, and availability impacts.

No prior access required.
Malicious website interaction.
High system compromise risk.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability in the Web Audio component could impact the behavior of the application and potentially lead to data corruption or denial of service. These issues could occur when users interact with malicious web content or files within supported applications. No specific types of sensitive data or PII are indicated as being at risk.

Application service behavior.
Malicious web content interaction.
Potential application instability.

Operational Fix

Recommended remediation, mitigation, and detection steps

The Web Audio component in Firefox and Thunderbird contains incorrect boundary conditions. Teams managing user endpoints or client application deployments are likely responsible for addressing this vulnerability. The first step is to inventory all instances of the affected software, confirm user reachability, and then plan for updates.

Application owners should own the issue.
Verify user adoption of recent versions.
Plan phased deployments of updates.

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 Web Audio component in Firefox and Thunderbird?

The Web Audio component is a built-in feature within Firefox and Thunderbird that enables the processing, synthesis, and analysis of audio signals directly within the browser or mail client. It allows web developers and email content creators to build sophisticated audio applications and rich media experiences that run locally on your device without needing external plugins.

What does CWE-119 mean for CVE-2026-2773?

CWE-119 refers to improper restriction of operations within the bounds of a memory buffer. In plain terms, the Web Audio component fails to properly verify the size of data before processing it. This weakness allows an attacker to manipulate the memory space, which could lead to application instability or allow unauthorized operations on your system if the software tries to write data beyond its designated area.

Do I need to be logged into a site to trigger this vulnerability?

No. An attacker does not need to authenticate or have prior access to your account to attempt exploitation. The vulnerability is triggered by having your application process malicious web content, such as visiting a compromised website. Note that simply having the software installed while it is idle or offline does not trigger the flaw; active interaction with malicious content is required.

Why does Halo Surface Signal rate this as unlikely to be external?

Halo Surface Signal notes that while Firefox and Thunderbird retrieve internet content, they are client-side applications, not public-facing network services or gateways. Because the affected Web Audio component resides on your local machine and is not a service listening for unsolicited connections from the internet, it is not categorized as a standard external attack surface.

How should I respond if I use Firefox or Thunderbird?

Your primary goal is to ensure you are running a patched version of the software. Start by checking your installed versions against the list of fixed releases, such as Firefox 148 or the corresponding ESR versions. If you manage multiple endpoints, use your software deployment tools to inventory instances and prioritize updating those that users frequently use to browse the web.

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.