CVE-2018-5721

Name: CVE-2018-5721
Creator: NVD / NIST
Published: 2018-01-17T06:29:00.277+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 1.95%

Last modified Jun 17, 2026

CVE-2018-5721 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. Stack-based buffer overflow in the ej_update_variables function in router/httpd/web.c on ASUS routers (when using software from https://github.com/RMerl/asuswrt-merlin) allows web authenticated attackers to execute code via a request that updates a setting. In ej_update_variables, the length of the variable action_script is not checked, as long as it includes a "_wan_if" substring.. EPSS estimates a 1.95% chance of exploitation in the next 30 days.

Description

Stack-based buffer overflow in the ej_update_variables function in router/httpd/web.c on ASUS routers (when using software from https://github.com/RMerl/asuswrt-merlin) allows web authenticated attackers to execute code via a request that updates a setting. In ej_update_variables, the length of the variable action_script is not checked, as long as it includes a "_wan_if" substring.

Metrics

CVSS 3.1

8.8/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

1.95%

77.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-787

Affected Software

Vendor	Product	Versions
Asuswrt-Merlin	Asuswrt-Merlin	<= 382.1_2

References

http://www.w0lfzhang.com/2018/01/17/ASUS-router-stack-overflow-in-http-server/Exploit, Third Party Advisory
http://www.w0lfzhang.com/2018/01/17/ASUS-router-stack-overflow-in-http-server/Exploit, Third Party Advisory

Timeline

Published: Jan 17, 2018
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2018-5721?

How severe is CVE-2018-5721?

CVE-2018-5721 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 1.95% probability of exploitation in the next 30 days.

How do I fix CVE-2018-5721?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2018-5721?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST