What is CVE-2017-20206?

CVE-2017-20206 is a critical-severity vulnerability in Wpmudev Appointments, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2025-10-18.

How severe is CVE-2017-20206?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Deserialization in Wpmudev Appointments

CVE-2017-20206

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.

Vulnerability class: Insecure Deserialization

EPSS: 0.007 (48.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Wpmudev Appointments — versions 0

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

References

security@wordfence.com (Third Party Advisory)
security@wordfence.com (Third Party Advisory, Press/Media Coverage)
security@wordfence.com (Patch)

Frequently asked questions

What is CVE-2017-20206?: CVE-2017-20206 is a critical-severity vulnerability in Wpmudev Appointments, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2025-10-18.
How severe is CVE-2017-20206?: Critical severity. CVSS v3 base score is 9.8 out of 10.