CVE-2026-49106: Contact Form 7 Auth Bypass Vulnerability

CVE-2026-49106 Overview

CVE-2026-49106 is an unauthenticated PHP Object Injection vulnerability in the WordPress plugin Integration for Contact Form 7 and Constant Contact, affecting versions up to and including 1.1.6. The flaw stems from insecure deserialization of attacker-controlled input [CWE-502]. Remote attackers can submit crafted serialized payloads without authentication, triggering object instantiation that may chain into arbitrary code execution, file operations, or data tampering when a suitable POP gadget is present in the WordPress runtime.

Critical Impact
An unauthenticated remote attacker can inject malicious PHP objects to compromise confidentiality, integrity, and availability of the WordPress site.

Affected Products

Integration for Contact Form 7 and Constant Contact plugin for WordPress
Versions less than or equal to 1.1.6
WordPress sites with the plugin installed and active

Discovery Timeline

2026-06-15 - CVE-2026-49106 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2026-49106

Vulnerability Analysis

The plugin passes untrusted input into PHP's unserialize() function or an equivalent deserialization routine without validating the data's origin or structure. PHP deserialization rebuilds objects from a serialized string and triggers magic methods such as __wakeup(), __destruct(), or __toString() during the process. When attacker-controlled data is deserialized, these magic methods execute against attacker-defined object properties.

In a WordPress environment, the plugin shares the runtime with WordPress core and other installed plugins. This creates a large surface of available classes for property-oriented programming (POP) chains. An attacker can craft a serialized payload that selects a vulnerable class, sets its properties, and chains gadgets to achieve file writes, SQL execution, or arbitrary command execution.

The vulnerability requires no authentication and no user interaction. The attack is reachable over the network through the plugin's request handlers.

Root Cause

The root cause is deserialization of untrusted input, classified under [CWE-502]. The plugin trusts data received through a request parameter, cookie, or stored option and feeds it directly to unserialize() without using safer alternatives such as json_decode() or applying the allowed_classes option introduced in PHP 7.

Attack Vector

The attacker sends an HTTP request to a plugin endpoint that processes serialized input. The payload contains a serialized PHP object referencing a gadget class available within the WordPress runtime. When the plugin deserializes the payload, the constructed object's magic methods execute the gadget chain. No credentials are required, and the exploit can be delivered through any network path that reaches the affected WordPress instance.

No verified public exploit code is currently available. Refer to the Patchstack Vulnerability Report for technical details.

Detection Methods for CVE-2026-49106

Indicators of Compromise

Inbound HTTP requests containing serialized PHP markers such as O: (object), a: (array), or s: (string) in POST bodies, cookies, or query parameters targeting plugin endpoints.
Unexpected PHP files written under wp-content/uploads/ or modifications to wp-config.php, theme, or plugin files.
New or modified WordPress administrator accounts and unexpected scheduled tasks in wp_options (cron).
PHP error log entries referencing unserialize(), __wakeup, or __destruct warnings tied to the affected plugin.

Detection Strategies

Inspect web server access logs for requests containing serialized object patterns directed at the cf7-constant-contact plugin paths.
Run file integrity monitoring on the WordPress installation to detect unauthorized changes to PHP files.
Deploy WAF rules that flag serialized PHP payloads in unauthenticated requests.
Correlate web request anomalies with subsequent process execution on the host using endpoint telemetry.

Monitoring Recommendations

Enable PHP error and access logging with retention sufficient for incident review.
Alert on outbound network connections originating from the PHP-FPM or web server process to unusual destinations.
Monitor for spawning of shell interpreters (sh, bash, cmd.exe) from the web server user account.

How to Mitigate CVE-2026-49106

Immediate Actions Required

Update Integration for Contact Form 7 and Constant Contact to a version newer than 1.1.6 once released by the vendor.
If a patched version is not yet available, deactivate and remove the plugin from affected WordPress sites.
Audit WordPress administrator accounts, scheduled cron events, and recently modified files for signs of post-exploitation.
Rotate WordPress secret keys in wp-config.php and reset administrator credentials on potentially exposed sites.

Patch Information

Consult the Patchstack Vulnerability Report for the vendor's remediation status and the fixed plugin version. Apply the update through the WordPress plugin manager or by replacing the plugin files directly on the server.

Workarounds

Block requests containing serialized PHP object patterns at the WAF or reverse proxy layer until patching is complete.
Restrict access to the plugin's request endpoints using IP allowlisting where feasible.
Disable the plugin until a patched release is verified in a staging environment.

bash

# Example ModSecurity rule to block serialized PHP object payloads
SecRule REQUEST_BODY|ARGS|REQUEST_COOKIES "@rx O:[0-9]+:\"[A-Za-z_\\\\]+\":[0-9]+:\{" \
    "id:1004910,phase:2,deny,status:403,log,\
    msg:'Possible PHP Object Injection (CVE-2026-49106)'"