CVE-2022-4120

Stop Spammers Security <= 2022.5 - Unauthenticated PHP Object Injection

2022-12-05 00:00
Seryeon Ham

Strategic Overview

Status
Patched in 2022.6
Affected Plugin
Stop Spammers Classic
Affected Version
<= 2022.5
CVSS
9.8Critical
Weakness type
CWE-502 · Deserialization of Untrusted Data
CVE
CVE-2022-4120
View all Stop Spammers Classic vulnerabilities

At a glance

CVE-2022-4120 is a critical-severity Deserialization of Untrusted Data vulnerability in the Stop Spammers Classic WordPress plugin, affecting versions <= 2022.5. It carries a CVSS score of 9.8 (reachable over the network; low attack complexity; high confidentiality, integrity, availability impact). Exploitation requires no authentication. The issue is fixed in version 2022.6; sites on affected versions should update now. Disclosed December 2022, reported by Seryeon Ham.

Vulnerability Overview

The Stop Spammers Security plugin for WordPress is vulnerable to PHP Object Injection in versions up to, and including, 2022.5 via deserialization of untrusted input when issuing a CPATCHA challenge. This allows unauthenticated attackers to inject a PHP Object. No POP chain is present in the vulnerable plugin. If a POP chain is present via an additional plugin or theme installed on the target system, it could allow the attacker to delete arbitrary files, retrieve sensitive data, or execute code. Note: The official PHP recommendation is not to pass untrusted input to unserialize even if the allowed_classes option is set to false.

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 privileges on the target site, 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

Reaching this weakness in Stop Spammers Classic <= 2022.5 takes no account at all. 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 Stop Spammers Classic the fix is 2022.6: builds <= 2022.5 are affected, anything from 2022.6 onward is not.

Remediation

Update to version 2022.6, or a newer patched version

How does WordSec protect against this?

Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: 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: Stop Spammers Classic 2022.6 closes this, and updating the plugin is the step that ends it.

  • Firewall
  • Scanner
  • Login Security

External References

https://www.cve.org/CVERecord?id=CVE-2022-4120https://www.wordfence.com/threat-intel/vulnerabilities/id/6065ad75-1685-4f1d-9ba9-d4c8ec840521https://nvd.nist.gov/vuln/detail/CVE-2022-4120

Related records

Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C