A new security weakness surfaced in Microsoft Edge (Chromium-based) earlier this year, tracked as CVE-2025-47181. In simple terms, Edge fails to properly check shortcut links (aka *symbolic links* or symlinks) before opening files, letting sneaky attackers access files or escalate privileges on your local computer. In this post, I’ll break down what’s going on, show you practical examples, and discuss potential attack methods — all in straightforward language.
What’s the Problem?
Whenever a program like Edge needs to open a file, it’s supposed to check if that file is actually what it looks like. If the file is a shortcut (symbolic link) pointing somewhere else, ideally, Edge should treat it differently or block access to risky locations.
With CVE-2025-47181, Microsoft Edge (Chromium-based editions, up to the patched version) allowed users — even those with limited rights — to use symlinks to trick Edge into opening or even changing sensitive local files. This is a classic *symlink following* or *improper link resolution* weakness.
Symlink Creation: The attacker plants a symbolic link somewhere Edge can reach.
2. Privilege Confusion: Edge believes it’s opening a harmless local file, but it’s actually accessing a sensitive file elsewhere (like in the Windows system folders).
3. Privilege Escalation: If Edge opens, writes to, or executes the tricked file, the attacker can take advantage.
Proof-of-Concept Exploit
Let’s walk through a basic PoC (proof of concept) scenario, illustrating how a local attacker could abuse this flaw. *All code and steps below are for educational awareness only.*
Suppose Edge allows you to install browser extensions from a local folder, which is supposed to be locked down (e.g., C:\Users\Public\EdgeExtensions). The attacker already has limited access to this folder.
Using a tool like mklink (built into Windows)
mklink C:\Users\Public\EdgeExtensions\hackfile.txt C:\Windows\System32\drivers\etc\hosts
This ties a file in the EdgeExtensions directory to the sensitive Windows hosts file.
Suppose Edge is started by a privileged user and tries to read/write/verify this file
const fs = require('fs');
const target = 'C:\\Users\\Public\\EdgeExtensions\\hackfile.txt';
// Edge thinks this is a safe local file, but it's the system hosts file!
fs.writeFileSync(target, 'malicious entry or data');
If Edge writes to or modifies hackfile.txt, it’s actually touching the hosts file, which could redirect traffic, block security updates, etc.
Privilege Escalation: Malicious code could run with higher rights than intended.
- Local File Disclosure/Overwrite: Sensitive files might be read, tampered with, or destroyed.
- System Manipulation: Attackers could change network settings, block security sites, or set up backdoors.
An attacker plants a symlink there pointing to a sensitive system or another user’s file.
- Edge, running with higher privileges (maybe from an admin login or scheduled task), interacts with the file as if it’s harmless.
- The attacker gains access, writes to, or executes the file, escalating their abilities on the machine.
Mitigations
Microsoft released a patch for this issue (see official advisory below). Users are urged to update Edge immediately. General advice:
Further Reading
- Microsoft Security Update Guide: CVE-2025-47181
- Symlink Attacks Explained (OWASP)
- mklink Command (Microsoft Docs)
Conclusion
CVE-2025-47181 is a classic reminder that *little things like file links* can open big doors. If you’re managing shared computers or developing extensions for Edge, pay special attention to file permissions and always follow least-privilege principles. Update Edge right away, and keep an eye on access controls in local directories.
Timeline
Published on: 05/22/2025 22:15:30 UTC
Last modified on: 05/29/2025 22:20:38 UTC