CVE-2026-0551

PPWP – Password Protect Pages <= 1.9.18 - Authenticated (Contributor+) PHP Object Injection via post_protection_roles

2026-08-22 10:47
Webbernaut

Strategic Overview

Status
Patched in 1.9.19
Affected Version
<= 1.9.18
CVSS
8.8High
Weakness type
CWE-502 · Deserialization of Untrusted Data
CVE
CVE-2026-0551
View all PPWP – Password Protect Pages vulnerabilities

At a glance

CVE-2026-0551 is a high-severity Deserialization of Untrusted Data vulnerability in the PPWP WordPress plugin, affecting versions <= 1.9.18. It carries a CVSS score of 8.8 (reachable over the network; low attack complexity; high confidentiality, integrity, availability impact). Exploitation requires an authenticated account at Contributor level or above. The issue is fixed in version 1.9.19; sites on affected versions should update now. Disclosed August 2026, reported by Webbernaut.

Vulnerability Overview

The PPWP – Password Protect Pages plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 1.9.18 via deserialization of untrusted input from the 'post_protection_roles' vulnerable parameter. This makes it possible for authenticated attackers, with Contributor-level access and above, to inject a PHP Object. No known POP chain is present in the vulnerable software, which means this vulnerability has no impact unless another plugin or theme containing a POP chain is installed on the site. If a POP chain is present via an additional plugin or theme installed on the target system, it may allow the attacker to perform actions like delete arbitrary files, retrieve sensitive data, or execute code depending on the POP chain present.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no interaction from a victim user. A successful exploit has high impact on confidentiality, integrity, availability — full site compromise territory.

CWE-502: Deserialization of Untrusted Data

PPWP <= 1.9.18 carries this weakness at post_protection_roles, and reaching it takes an account at Contributor level or above. Deserialization of untrusted data means the application reconstructs objects from input a caller controls, letting the attacker choose which classes get instantiated and what their properties hold.

A workable chain turns deserialization into file writes, deletions or code execution, depending on what the loaded classes do in their magic methods. For PPWP the fix is 1.9.19: builds <= 1.9.18 are affected, anything from 1.9.19 onward is not.

Remediation

Update to version 1.9.19, or a newer patched version

How does WordSec protect against this?

An attacker needs Contributor access first, so the firewall sees the attempt as traffic from a logged-in account: WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. None of that substitutes for the fix: PPWP 1.9.19 closes this, and updating the plugin is the step that ends it.

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External References

Related records

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