Easy!Appointments: Authorization bypass in Google OAuth provider binding lets any backend user rebind a peer provider's Google sync

published 2026-07-14 3 mo ago modified 2026-10-24 15 d ago also GHSA-8hm4-r66f-29wr , EUVD-2026-43723

cvss: 3.1; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 10%
public exploits: 0; none known

Easy!Appointments is a self hosted appointment scheduler. In versions prior to 1.6.0, `Google::oauth` at `application/controllers/Google.php:278` stores its URL-supplied `provider_id` in the session, and `oauth_callback` saves the issued Google OAuth token against that row without checking the caller owns the provider. Any logged-in backend user (admin, provider, or secretary) rebinds a peer provider's Google sync to a Google account they control. The peer's appointments then sync into the attacker's calendar with each customer's name and email attached as attendee data. Version 1.6.0 patches the issue.

Patch / fix

links 2

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 3 mo ago (2026-07-14)

Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 10% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/alextselegidis/easyappointments/security/advisories/GHSA-8hm4-r66f-29wr referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	3.1	CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:N
GitHub	3.1	3.1	CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
packagist	alextselegidis/easyappointments	<=1.5.2	no fix listed

Affected products

alextselegidis easyappointments

Classification

Weakness

CWE-639 Authorization Bypass Through User-Controlled Key

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary