Google Chrome on Android Intent Insufficient Validation Open Redirect Vulnerability (CVE-2021-38000, CISA KEV)
Executive & SecOps Summary
SECOPS ASSESSMENTGoogle Chrome on Android prior to version 95.0.4638.69
Remote attackers can force the browser to navigate to arbitrary malicious URLs via crafted HTML pages, leading to credential phishing or drive-by downloads
Immediately update Google Chrome on Android to the latest version (95.0.4638.69 or higher) via the Google Play Store
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Users must update Google Chrome via the Google Play Store. For enterprise environments utilizing Mobile Device Management (MDM) or ADB, administrators can verify and force updates using the following commands:
# Verify the installed Chrome version on the connected Android device
adb shell dumpsys package com.android.chrome | grep versionName
# Force stop Chrome and redirect the user to the Play Store update page
adb shell am force-stop com.android.chrome
adb shell am start -a android.intent.action.VIEW -d 'market://details?id=com.android.chrome'2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, enforce strict web filtering policies on corporate firewalls or secure web gateways (SWG) to block suspicious outbound Intent-based redirections.
# Example: Block known malicious redirection domains in local DNS configuration (BIND9)
# Add the following to /etc/bind/named.conf.local
zone 'suspicious-intent-redirect.com' {
type master;
file '/etc/bind/db.blocked';
};3. Log Audit & IoC Verification Commands
Administrators can inspect Android system logs via ADB to detect anomalous Intent resolutions or redirection behaviors initiated by Chrome.
# Monitor real-time logs for Chrome Intent handling and redirection activities
adb logcat | grep -E 'IntentResolver|ChromeTabbedActivity|Redirect'Block Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2021-38000) exists due to insufficient validation of untrusted input within the Intent handling mechanism of Google Chrome on Android. Android uses Intents for inter-process communication, allowing web applications to trigger external apps or redirect users via the 'intent://' URI scheme. Chrome failed to properly validate and sanitize parameters within these Intents (CWE-20, CWE-601), allowing an attacker to bypass security controls and force the browser to redirect to an arbitrary, untrusted destination.
2. Exploitation Mechanics & Attack Scenario
An attacker exploits this vulnerability by hosting a specially crafted HTML page containing malicious Intent links or scripts. When a victim visits this page, the browser processes the 'intent://' scheme. If the Intent contains a malicious fallback URL parameter (such as 'S.browser_fallback_url'), Chrome processes the redirection without adequate validation, forcing the user's browser session to navigate to the attacker-controlled malicious site. Because this occurs seamlessly within the browser context, users are highly susceptible to phishing.
3. Infrastructure & Business Impact
As a vulnerability listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, this flaw has been actively exploited in the wild. In an enterprise environment, successful exploitation can lead to credential theft via highly convincing phishing pages mimicking internal corporate portals. Furthermore, it can serve as an initial access vector for mobile malware delivery, compromising corporate data and endpoint security.
Official Vendor Advisories & References
Insufficient validation of untrusted input in Intents in Google Chrome on Android prior to 95.0.4638.69 allowed a remote attacker to arbitrarily browser to a malicious URL via a crafted HTML page.
Frequently Asked SecOps Questions (CVE-2021-38000)
FAQQ1. How critical is CVE-2021-38000 and is it actively exploited in the wild?
CVE-2021-38000 is rated CVSS 6.1 (MEDIUM) with a 30-day EPSS exploitation probability of 5.0%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2021-38000?
Primary impacted vendors include google across chrome. Scope summary: All versions of Google Chrome on Android prior to 95.0.4638.69
Q3. What temporary mitigations or workarounds exist for CVE-2021-38000 before patching?
[Mitigation] Immediately update Google Chrome on Android to the latest version (95.0.4638.69 or higher) via the Google Play Store Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
Generate an Internal Engineering Notice or CISO Report for CVE-2021-38000
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