Zyxel security advisory for remote code execution and denial-of-service vulnerabilities of CPE
CVE: CVE-2025-7673
Summary
Zyxel has released firmware updates that address a buffer overflow vulnerability causing denial-of-service (DoS) and potential remote code execution (RCE) issues affecting certain CPE models. Customers are strongly advised to install these updates to ensure optimal protection.
What is the vulnerability?
The buffer overflow vulnerability in the URL parser of the zhttpd web server on certain CPE models could allow an unauthenticated attacker to cause DoS conditions and potentially execute arbitrary code by sending a specially crafted HTTP request.
What products are vulnerable—and what should you do?
After a thorough investigation, we have identified the vulnerable CPE that are within their warranty and support period and are releasing firmware patches to address the issue, as shown in the table below.
Please note that the table does NOT include customized models for internet service providers (ISPs). For ISP customers, please contact your Zyxel representative for further details. For users who purchased the listed devices on their own, please contact your local Zyxel support team for the new firmware file to ensure optimal protection.
| Affected models | Patch available in |
|---|---|
| EMG3525-T50B |
|
| EMG5523-T50B |
|
| EMG5723-T50K | V5.50(ABOM.5)C0 in Dec 2020 |
| EMG6726-B10A | V5.13 (ABNP.6).C0 in Feb 2021 |
| EX3510-B0 | V5.17(ABUP.3)C0 in Mar 2021 |
| EX5510-B0 | V5.15(ABQX.3)C0 in Jan 2021 |
| VMG1312-T20B | V5.50(ABSB.3)C0 in Dec 2020 |
| VMG3625-T50B | V5.50(ABPM.4)C0 in Dec 2020 |
| VMG3925-B10B/B10C | V5.13(AAVF.16)C0 in Dec 2020 |
| VMG3927-B50A_B60A | V5.15(ABMT.5)C0 in Dec 2020 |
| VMG3927-B50B | V5.13(ABLY.6)C0 in Feb 2021 |
| VMG3927-T50K | V5.50(ABOM.5)C0 in Dec 2020 |
| VMG4005-B50B | V5.13(ABRL.5)C0 in Q3 2021 |
| VMG4927-B50A | V5.13(ABLY.6)C0 in Feb 2021 |
| VMG8623-T50B | V5.50(ABPM.4)C0 in Dec 2020 |
| VMG8825-B50A_B60A | V5.15(ABMT.5)C0 in Dec 2020 |
| VMG8825-Bx0B | V5.17(ABNY.5)C0 in Dec 2020 |
| VMG8825-T50K | V5.50(ABOM.5)C0 in Dec 2020 |
| VMG8924-B10D | V5.13(ABGQ.6)C0 in Dec 2020 |
| XMG3927-B50A | V5.15(ABMT.5)C0 in Dec 2020 |
| XMG8825-B50A | V5.15(ABMT.5)C0 in Dec 2020 |
Got a question or a tipoff?
Please contact your local service rep for further information or assistance. If you’ve found a vulnerability, we want to work with you to fix it—contact security@zyxel.com.tw and we’ll get right back to you.
Acknowledgment
Thanks to Thomas Rinsma for reporting the issues to us.
Revision history
2020-12-17: Initial release
2021-01-29: Corrected the patch firmware version of VMG8825-Bx0B
2025-07-16: Updated the CVE ID and vulnerability description