The flaw in OpenReception’s bootstrap booking flow permits an attacker to perform a minimal Proof‑of‑Work challenge, obtain a bearer token, and then use that token to schedule appointments in private channels (isPublic = false) without any authentication. The token is not bound to channel identifiers, and the service fails to enforce a check for channel.isPublic during the new‑client path, allowing the creation of confirmed or new appointments on channels that should be inaccessible. This results in unauthorized, often unconfirmed appointments that compromise patient privacy and can overwhelm channel resources.

Affected systems include OpenReception appointment booking software, versions 1.0.1 and earlier. The vulnerability resides in the bootstrap‑challenge, bootstrap‑verify, and create‑new‑client sequence and is enabled by the absence of a channel.isPublic guard. No patched versions are available as of publication; all installations that have not upgraded from these versions remain vulnerable.

The CVSS score of 6.5 denotes moderate severity. Exploitation is trivial: a 16‑bit Proof‑of‑Work challenge is solved in less than one second on commodity hardware, the service does not rate‑limit beyond a generic throttle store, and any private channel identifier can be supplied to the create‑new‑client endpoint. The vulnerability is not listed in CISA KEV catalog. An attacker can gain immediate access to private channels and schedule unauthorized appointments, potentially disrupting availability and compromising confidential information.