CVE-2026-16404: Firefox for Android Spoofing Vulnerability

CVE-2026-16404 Overview

CVE-2026-16404 is a spoofing vulnerability affecting Mozilla Firefox for Android. Mozilla fixed the issue in Firefox 153 and documented it in security advisory MFSA-2026-68. The weakness maps to [CWE-290] Authentication Bypass by Spoofing, indicating that an attacker can present misleading trust indicators to a user through the mobile browser.

The vulnerability requires user interaction over the network and produces a scope change with high impact to integrity. Because the attack targets what the user sees and trusts, successful exploitation can facilitate phishing, credential theft, and drive-by delivery of malicious content that appears to originate from a legitimate origin.

Critical Impact
Attackers can craft web content that spoofs trusted origins or UI elements in Firefox for Android, undermining the browser's integrity guarantees and enabling downstream phishing and credential theft.

Affected Products

Mozilla Firefox for Android prior to version 153
Android mobile devices running vulnerable Firefox builds
Users of Firefox for Android who visit attacker-controlled web content

Discovery Timeline

2026-07-21 - CVE-2026-16404 published to the National Vulnerability Database
2026-07-22 - Entry last modified in NVD

Technical Details for CVE-2026-16404

Vulnerability Analysis

CVE-2026-16404 is classified under [CWE-290] as an authentication bypass by spoofing. In the context of a mobile browser, spoofing weaknesses typically allow attacker-controlled content to imitate trusted browser chrome, address bar contents, security indicators, or origin information. The victim sees content that appears to belong to a legitimate site while the actual origin is attacker-controlled.

The attack executes over the network and requires the victim to interact with malicious content, such as tapping a link or loading a crafted page. Exploitation produces a scope change, meaning the impact extends beyond the vulnerable component to affect resources under a different security authority. Confidentiality and availability are not directly affected, but integrity impact is high because the user's trust decisions are manipulated.

Mozilla addressed the flaw in Firefox 153. Full technical details are tracked in Mozilla Bugzilla Report #2020253 and the Mozilla Security Advisory MFSA-2026-68.

Root Cause

The root cause is improper validation or rendering logic that permits attacker-controlled content to influence how origin, identity, or security state is presented to the user. Public advisories do not disclose specific implementation details beyond the CWE classification and the fixed version.

Attack Vector

An attacker hosts a crafted page or delivers a crafted link through email, messaging, or advertising. When a Firefox for Android user loads the page and interacts with it, the browser presents misleading UI or origin cues. The user then discloses credentials, approves an action, or downloads content believing it is served by a trusted site.

No verified proof-of-concept code has been published. Refer to Mozilla's advisory for the authoritative fix description.

Detection Methods for CVE-2026-16404

Indicators of Compromise

Firefox for Android installations reporting a version earlier than 153 in mobile device inventory data
Outbound traffic from mobile devices to domains newly registered or associated with phishing infrastructure
User reports of Firefox displaying inconsistent address bar content, unexpected origin prompts, or credential entry on sites that appear legitimate

Detection Strategies

Query mobile device management (MDM) and unified endpoint management (UEM) telemetry for Firefox for Android build numbers below 153
Correlate mobile web proxy logs with threat intelligence feeds to surface access to known phishing or spoofing infrastructure
Review authentication logs for successful logins from mobile user agents shortly after visits to suspicious URLs

Monitoring Recommendations

Track Firefox for Android version distribution across the fleet and alert on installs that fall behind the current release
Monitor identity providers for anomalous mobile logins that follow link clicks in email or messaging platforms
Enable browser telemetry and crash reporting where policy permits to surface anomalies in rendering behavior

How to Mitigate CVE-2026-16404

Immediate Actions Required

Update Firefox for Android to version 153 or later through Google Play or the Mozilla distribution channel used in your environment
Push the updated Firefox build through MDM to enrolled Android devices and enforce minimum version policies
Notify mobile users about spoofing risks and reinforce guidance to verify URLs and certificate details before submitting credentials

Patch Information

Mozilla fixed CVE-2026-16404 in Firefox 153. Details are published in the Mozilla Security Advisory MFSA-2026-68 and tracked in Mozilla Bugzilla Report #2020253. Apply the update through the Google Play Store or your managed application deployment pipeline.

Workarounds

Restrict use of Firefox for Android on managed devices until the update to version 153 is confirmed
Route mobile browsing through a filtering proxy that blocks known phishing and spoofing infrastructure
Enforce phishing-resistant authentication such as FIDO2 security keys or platform passkeys so that spoofed origins cannot capture reusable credentials

bash

# Example: enforce minimum Firefox for Android version via MDM policy (Android Enterprise managed configuration)
# Replace <MDM_CLI> with your management platform's command-line tool
<MDM_CLI> app-policy set \
  --package org.mozilla.firefox \
  --min-version-code 153 \
  --action block-if-below \
  --group all-mobile-devices