CVE-2017-20208

CriticalRCE

Published: 18 October 2025

Published

18 October 2025

Modified

19 December 2025

KEV Added

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Patch

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CVSS Score 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0054 67.8th percentile

Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2017-20208 is a critical-severity Deserialization of Untrusted Data (CWE-502) vulnerability in Metagauss Registrationmagic. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 32.2% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match

prevent

Requires timely patching of the specific PHP Object Injection flaw in the RegistrationMagic plugin via deserialization in is_expired_by_date(), as fixed in version 3.7.9.3.

SI-10 Information Input Validation good match

prevent

Enforces validation of untrusted input prior to deserialization, directly blocking malicious PHP Object Injection payloads exploited by unauthenticated attackers.

SI-7 Software, Firmware, and Information Integrity partial match

detect

Verifies software and information integrity to detect unauthorized changes, such as remote files fetched and installed via the POP chain leading to RCE.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1505.003 Web Shell Persistence

Adversaries may backdoor web servers with web shells to establish persistent access to systems.

attack.mitre.org →

Why these techniques?

Unauthenticated remote PHP Object Injection in public-facing WordPress plugin enables T1190 (Exploit Public-Facing Application); POP chain facilitates remote file fetch/install for RCE like webshell (T1100).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

NVD Description

The RegistrationMagic – Custom Registration Forms, User Registration, Payment, and User Login plugin for WordPress is vulnerable to PHP Object Injection in all versions up to 3.7.9.3 (exclusive) via deserialization of untrusted input from the is_expired_by_date() function. This makes it…

possible for unauthenticated attackers to inject a PHP Object. The additional presence of a POP chain allows attackers to fetch a remote file and install it on the site.

Deeper analysisAI

CVE-2017-20208 is a PHP Object Injection vulnerability (CWE-502) affecting the RegistrationMagic – Custom Registration Forms, User Registration, Payment, and User Login plugin for WordPress in all versions up to, but excluding, 3.7.9.3. The issue arises from deserialization of untrusted input in the is_expired_by_date() function, enabling attackers to inject a PHP Object. The vulnerability carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating critical severity due to its potential for high impact on confidentiality, integrity, and availability.

Unauthenticated attackers can exploit this vulnerability remotely with low complexity and no user interaction required. By supplying malicious input, they can trigger PHP Object Injection, and the presence of a Proof-of-Concept (POP) chain allows them to fetch a remote file and install it on the targeted site, potentially leading to remote code execution, such as deploying a webshell.

Advisories from Wordfence highlight the availability of a patch in the WordPress plugin trac at changeset 1733274, which addresses the deserialization issue. Security practitioners should urge site administrators to update the RegistrationMagic plugin to version 3.7.9.3 or later to mitigate the vulnerability, as detailed in the referenced threat intelligence and blog posts.

This vulnerability was among three zero-day plugin flaws exploited in the wild, as reported by Wordfence in 2017, underscoring its real-world impact prior to formal CVE assignment.