CVE-2025-8041: Firefox Android URL Spoofing Vulnerability

CVE-2025-8041 Overview

CVE-2025-8041 affects Firefox for Android, where the address bar truncated URLs from the end rather than prioritizing the origin. This behavior allowed attackers to craft URLs that hid the true origin from users by pushing it off-screen. The issue maps to [CWE-451] User Interface Misrepresentation of Critical Information and enables phishing and address bar spoofing scenarios. Mozilla fixed the flaw in Firefox 141.

Critical Impact
Attackers can construct long URLs that visually conceal the origin domain in the mobile address bar, enabling convincing phishing attacks against Firefox for Android users.

Affected Products

Mozilla Firefox for Android (versions prior to 141)
Google Android platform hosting affected Firefox builds
Mobile browser deployments relying on the Firefox address bar for origin verification

Discovery Timeline

2025-08-19 - CVE-2025-8041 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database
Mozilla Advisory - Documented in Mozilla Security Advisory MFSA-2025-56

Technical Details for CVE-2025-8041

Vulnerability Analysis

The vulnerability resides in the address bar rendering logic of Firefox for Android. When a URL exceeded the visible width of the address bar, Firefox truncated the string from the end rather than preserving the origin. As a result, the origin, which is the security-critical portion of a URL, could be pushed out of view. Users relying on the address bar to verify the site they visited saw only the leading path or subdomain segments.

Attackers can craft URLs that place attacker-controlled subdomains or path segments at the beginning, followed by padding that pushes the real origin off-screen. For example, a URL beginning with login.bank.example.com. followed by a lengthy attacker path can make the address bar appear to display a trusted brand while the actual origin sits at an attacker-controlled domain.

Root Cause

The root cause is a user interface design flaw in URL rendering. Modern browsers prioritize the effective top-level domain plus one label (eTLD+1) when truncating URLs, keeping the origin visible. Firefox for Android instead applied simple end-of-string truncation, breaking the security assumption that the address bar reliably communicates origin.

Attack Vector

Exploitation requires only that a victim visit an attacker-controlled URL in Firefox for Android. No user interaction beyond normal browsing is needed. The attacker distributes crafted links through email, messaging apps, malvertising, or search engine optimization. Once loaded, the address bar visually misrepresents the origin, supporting credential phishing or malware delivery pages that impersonate trusted brands.

See the Mozilla Bug Report #1670725 for technical background on the truncation behavior.

Detection Methods for CVE-2025-8041

Indicators of Compromise

Mobile web traffic from Firefox for Android user agents to newly registered domains containing brand-like subdomain patterns such as paypal.com.attacker.tld
URLs with unusually long paths or subdomain chains delivered via SMS, email, or chat platforms to Android users
Credential submissions from Android Firefox clients to domains that do not match the impersonated brand

Detection Strategies

Inspect proxy and DNS logs for Android Firefox user agents connecting to domains whose lexical structure suggests brand impersonation through prepended subdomains
Correlate phishing report submissions from mobile users with Firefox for Android versions below 141 in endpoint inventory data
Hunt for outbound HTTP POST requests carrying credential-like form fields from mobile browsers to low-reputation domains

Monitoring Recommendations

Track Firefox for Android version distribution across managed mobile devices and flag any client below 141
Alert on user reports of suspicious mobile browsing sessions where the displayed site name did not match the actual destination
Monitor threat intelligence feeds for phishing kits explicitly targeting mobile browser URL truncation weaknesses

How to Mitigate CVE-2025-8041

Immediate Actions Required

Upgrade Firefox for Android to version 141 or later on all managed and personal devices
Push the update through mobile device management (MDM) policies to enforce compliance across the fleet
Notify users, particularly high-risk roles, to verify URLs by tapping the address bar to reveal the full string before entering credentials

Patch Information

Mozilla addressed CVE-2025-8041 in Firefox 141. Details are available in the Mozilla Security Advisory MFSA-2025-56. The fix changes address bar rendering to prioritize the origin when truncating long URLs.

Workarounds

Advise Android users to tap the address bar to expand the full URL before submitting sensitive information
Deploy mobile threat defense or DNS filtering to block known phishing domains at the network layer
Use password managers that autofill credentials based on origin matching, since they refuse to fill on mismatched domains

bash

# Example MDM compliance check for Firefox for Android version
adb shell dumpsys package org.mozilla.firefox | grep versionName
# Ensure versionName is 141 or higher; otherwise trigger update workflow