CVE-2017-20206

Appointments <= 2.2.1 - Unauthenticated PHP Object Injection

9.8 Critical

The Appointments plugin for WordPress is vulnerable to PHP Object Injection in versions up to, and including, 2.2.1 via deserialization of untrusted input from the wpmudev_appointments cookie. This allows unauthenticated attackers to inject a PHP Object. Attackers were actively exploiting this vulnerability with the WP_Theme() class to create backdoors.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: High
Integrity: High
Availability: High

Exploit likelihood

0.73%Up 0.7 points since Oct 18, 2025

What each source reports

CVE List Score used 9.8

Appointments <= 2.2.1 - Unauthenticated PHP Object Injection

Record: CVE-2017-20206
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness: CWE-502
Updated: 2026-11-02

EUVDEUVD-2017-18924 9.8

Record: EUVD-2017-18924
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-02

GitHub AdvisoriesGHSA-7mpm-gf56-q8wv 9.8

The Appointments plugin for WordPress is vulnerable to PHP Object Injection in versions up to,...

Record: GHSA-7mpm-gf56-q8wv
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness: CWE-502
Updated: 2026-11-02

NVD 9.8

Record: CVE-2017-20206
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness: CWE-502
Updated: 2026-11-02

Affected products

wpmudev appointments

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2017-20206 is a critical vulnerability (CVSS 9.8) in Wpmudev Appointments, published October 18, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.73%, the 54th percentile. No source names a fixed version.