# CVE-2026-36606: Mercusys AC12G hardcoded DES key in configuration backup

Source: https://junglewise.ai/threats/cve-2026-36606-mercusys-ac12g-hardcoded-des-key-in-configuration-backup  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-03. Updated: 2026-06-03  
License: CC BY 4.0 with a link back

CVE-2026-36606 · Severity: info · CVSS 7.4 · Published 2026-06-03

The Mercusys AC12G router uses a weak, hardcoded password to encrypt its configuration backup files. If an attacker obtains one of these backup files, they can easily decrypt it to reveal sensitive information such as the administrator password, Wi-Fi keys, and internet service credentials. This could lead to a full takeover of the device and the local network it manages.

Technologies: [Mercusys AC12G](https://junglewise.ai/threats/technologies/ac12g). Vendors: [Mercusys](https://junglewise.ai/threats/vendors/mercusys).

## Quick answers

**Is CVE-2026-36606 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-36606 being exploited in the wild.

**How severe is CVE-2026-36606?** Informational severity, with a CVSS score of 7.4, published 3 June 2026.

**Which products and versions are affected?** Mercusys AC12G AC12G(EU)_V1_200909, AC12G(EU)_V1_210128.

**Is there a fix for CVE-2026-36606?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-36606 attacked?** It is attacked with local access, in a network appliance.

**Am I affected by CVE-2026-36606?** Check whether you run Mercusys AC12G at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The configuration backup/restore module in Mercusys AC12G (EU) V1 firmware (specifically versions 200909 and 210128) utilizes a hardcoded DES key (0x478DA50BF9E3D2CF) in ECB mode. The encryption process involves proprietary TP-Link LZ compression followed by single DES-ECB encryption with a 16-byte 'SDMP_CONF_V004' header. Because the key is static and shared across multiple TP-Link and Mercusys product lines, an attacker who obtains a backup file can decrypt it without further authentication. Decrypted contents include plaintext admin passwords, WPA2 pre-shared keys, PPPoE credentials, and DDNS account details. No fix is planned as the product is reportedly end-of-life.

## Affected products

- Mercusys AC12G (EU) V1 AC12G(EU)_V1_200909, AC12G(EU)_V1_210128

## Timeline

- 2026-06-03: disclosed
- 2026-06-03: advisory

## References

- [https://github.com/Tymbark7372/MERCUSYS-AC12G/blob/master/advisories/CVE-2026-36606.md](https://github.com/Tymbark7372/MERCUSYS-AC12G/blob/master/advisories/CVE-2026-36606.md)

## Related threats

- [Mercusys AC12G hardcoded WiFi credentials in firmware](https://junglewise.ai/threats/cve-2026-36616-mercusys-ac12g-hardcoded-wifi-credentials-in-firmware)
- [Mercusys AC12G information disclosure in /agileconfigreset endpoint](https://junglewise.ai/threats/cve-2026-36615-mercusys-ac12g-information-disclosure-in-agileconfigreset)
- [Mercusys AC12G uninitialized buffer disclosure in UPnP](https://junglewise.ai/threats/cve-2026-36611-mercusys-ac12g-uninitialized-buffer-disclosure-in-upnp)
- [Mercusys AC12G V1 password recovery via static nonce and weak encoding](https://junglewise.ai/threats/cve-2026-36609-mercusys-ac12g-v1-password-recovery-via-static-nonce-and-weak)
- [Mercusys AC12G UPnP port forwarding to local admin interface](https://junglewise.ai/threats/cve-2026-36608-mercusys-ac12g-upnp-port-forwarding-to-local-admin-interface)