CVE-2025-21399
📋 TL;DR
This vulnerability in Microsoft Edge (Chromium-based) allows an attacker to elevate privileges on a compromised system. It affects users running vulnerable versions of Microsoft Edge on Windows systems. Successful exploitation could enable attackers to execute code with higher privileges than intended.
💻 Affected Systems
- Microsoft Edge (Chromium-based)
📦 What is this software?
Edge Update by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
An attacker could gain SYSTEM-level privileges on a compromised Windows machine, enabling complete system takeover, data theft, and lateral movement within the network.
Likely Case
Local privilege escalation allowing attackers to bypass security controls, install malware, or access restricted resources on the compromised system.
If Mitigated
With proper patch management and least privilege principles, impact is limited to the user context without escalation to higher privilege levels.
🎯 Exploit Status
Exploitation requires local access to the system. The vulnerability is in the update mechanism, suggesting complex exploitation chain.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Microsoft Edge version containing the February 2025 security updates
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21399
Restart Required: No
Instructions:
1. Open Microsoft Edge. 2. Click Settings (three dots) → Help and feedback → About Microsoft Edge. 3. Edge will automatically check for and install updates. 4. Restart Edge if prompted.
🔧 Temporary Workarounds
Disable automatic updates
allPrevents the vulnerable update mechanism from being exploited, but leaves system unpatched against other vulnerabilities
Not recommended as it creates other security risks
🧯 If You Can't Patch
- Implement application control policies to restrict unauthorized Edge updates
- Enforce least privilege principles to limit damage from privilege escalation
🔍 How to Verify
Check if Vulnerable:
Check Microsoft Edge version in Settings → Help and feedback → About Microsoft Edge. If version is older than February 2025 security update, system is vulnerable.Check Version:
Start Microsoft Edge and navigate to edge://settings/help or check version in About Microsoft EdgeVerify Fix Applied:
Verify Microsoft Edge version is 120.0.2210.91 or later (or the specific version mentioned in Microsoft's security advisory).📡 Detection & Monitoring
Log Indicators:
- Unusual Edge update processes running with elevated privileges
- Suspicious child processes spawned from Edge update mechanism
Network Indicators:
- Unexpected network connections from Edge update components to unusual destinations
SIEM Query:
Process creation events where parent process is Edge update component (msedgeupdate.exe) creating unexpected child processes with elevated privileges🔗 References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21399
- https://www.vicarius.io/vsociety/posts/elevation-of-privilege-vulnerability-in-microsoft-edge-chromium-based-detection-script
- https://www.vicarius.io/vsociety/posts/elevation-of-privilege-vulnerability-in-microsoft-edge-chromium-based-mitigation-script
