An undocumented endpoint, /agileconfigreset, in the Mercusys AC12G (EU) V1 firmware reveals internal buffer contents when accessed by an unauthenticated client on the same network. The returned data can include sensitive configuration information and potentially expose authentication credentials or other proprietary information. Because no authentication is required, an attacker who can reach the device locally can read this data and potentially use it for further exploitation.

Mercusys AC12G (EU) V1 running firmware AC12G(EU)_V1_200909. The flaw is specific to this version of the firmware; no other affected versions are mentioned in the advisory.

The CVSS score is 4.3, EPSS score is not available, and the vulnerability is not in the CISA KEV catalog. The lack of authentication combined with the leakage of internal buffer data makes this a serious information‑disclosure risk that is exploitable from any host on the adjacent local network. An attacker needs only network access and no credentials to trigger the vulnerability, implying high operational risk for devices in untrusted networks.