The vulnerability in the DDNS update function of the ASUSTOR ADM module allows a remote attacker to bypass proper TLS certificate validation. By forging or manipulating the certificate presented by the DDNS server, the attacker can conduct a Man‑in‑the‑Middle attack and capture sensitive data exchanged during the update, including the user’s account e‑mail, MD5 hashed password, and the device’s serial number. This is a severe confidentiality breach that could enable further compromise of the NAS device.

ASUSTOR ADM software versions 4.1.0 through 4.3.3.ROF1 and 5.0.0 through 5.1.1.RCI1 are affected. Newer releases beyond 5.1.1.RCI1 are presumed to have resolved the issue.

The CVSS score of 8.9 classifies the flaw as High severity, yet the EPSS score of less than 1% indicates a low exploitation probability. The flaw is not currently listed in the CISA KEV catalog. The attack vector is inferred to be remote network; an adversary would need the ability to trigger a DDNS update over HTTPS, then supply a tampered certificate to a passive attacker. Successful exploitation would grant an attacker confidentiality gain but would not transpire without the specific DDNS update scenario.