External risk intelligence

Firefox for Android Download Restriction Bypass

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2025-8042

The vulnerability affects client-side browser functionality within Firefox for Android, specifically regarding sandbox attribute enforcement for downloads. It requires a user to navigate to a malicious web page via the browser, rather than the browser itself serving as a public-facing network service or internet-exposed gateway.

Mozilla Firefox

before 141.0

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 issue concerns a vulnerability in Firefox for Android that could allow unauthorized downloads to start, even when the browser's security settings intended to prevent them. While a fix is available, its primary business implication at this moment is confirming whether this specific technology is in use and potentially exposed.

Sandbox download control was bypassed.
Affects mobile browser user experience.
Confirm relevance and confirm exposure.

Attack Path

How an attacker could exploit the issue

An attacker could leverage this vulnerability by tricking a user into visiting a malicious website using a vulnerable version of Firefox for Android. The website would embed a sandboxed iframe that lacks the necessary permissions to initiate downloads. By exploiting the flaw, the attacker could bypass the sandbox restrictions, allowing the iframe to trigger a download without explicit user consent, potentially leading to the execution of malicious software.

Requires user visit to malicious site.
Malicious iframe bypasses download restrictions.
Risk of unauthorized downloads and code execution.

Live Threat

Current exploitation, exposure, and threat context

When supported by the advisory, a sandboxed iframe in Firefox for Android, even without explicit download permissions, could initiate downloads. This may affect system data by allowing unauthorized file transfers to the user's device.

System data could be affected.
Unauthorized downloads may occur.
Sensitive information could be exposed.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability impacts users of Firefox for Android. The first practical move is for security teams to identify devices running affected versions of Firefox for Android and confirm their exposure to malicious websites. Following this, application owners and platform teams should coordinate remediation efforts, prioritizing business-critical devices and user impact.

Mobile platform owners should manage this issue.
Verify affected Firefox for Android versions.
Plan updates during scheduled maintenance.

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 Firefox for Android?

Firefox for Android is a mobile web browser developed by Mozilla that provides users with a platform to navigate the internet, render web content, and manage online sessions on Android devices. It employs various security mechanisms, including sandbox restrictions, to isolate web components and ensure that websites cannot perform unauthorized actions on the user's device or access system resources without appropriate permissions.

What does CVE-2025-8042 mean?

This CVE refers to a security weakness classified under CWE-732, which deals with incorrect permission assignment for critical resources. In the context of CVE-2025-8042, the browser fails to correctly enforce the sandbox attributes of an iframe. Because the browser does not properly check for the 'allow-downloads' permission, it inadvertently grants a restricted sub-component the power to bypass standard security policies and initiate file downloads without authorization.

How is this vulnerability triggered?

An attacker triggers this flaw by luring a user to a malicious webpage that contains a specifically crafted sandboxed iframe. The vulnerability is activated when the browser processes this iframe and ignores the absence of the 'allow-downloads' attribute. It is important to note that simply having the browser installed does not trigger the bug; it requires active user interaction with a site designed to exploit this specific gap in the sandbox enforcement.

Is my device at risk based on Halo Surface Signal?

According to Halo Surface Signal, this risk is considered 'Very unlikely' for most corporate environments. The vulnerability is client-side, meaning it is not a network-exposed service or gateway that an attacker can target remotely. Instead, risk is entirely dependent on a user's web browsing habits and their decision to visit an untrusted or malicious site, rather than a direct, unprompted attack on your infrastructure.

How do I address this browser issue?

To secure your devices, you should first identify any mobile hardware running a version of Firefox for Android older than 141. Once identified, ensure these devices are updated to the latest available version through the official app store. Coordinate with your mobile device management teams to prioritize these updates, ensuring that users have the corrected software that properly enforces download sandbox restrictions.

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.