CVE-2026-49763: Contact Form 7 HubSpot Auth Bypass Flaw

CVE-2026-49763 Overview

CVE-2026-49763 is an unauthenticated PHP Object Injection vulnerability in the Integration for Contact Form 7 HubSpot WordPress plugin. The flaw affects all versions up to and including 1.3.7. Attackers can deserialize attacker-controlled data without authentication, triggering arbitrary object instantiation within the PHP runtime. The issue is categorized under [CWE-502] Deserialization of Untrusted Data. When combined with a suitable POP (Property-Oriented Programming) gadget chain in the WordPress core or other installed plugins, this primitive enables remote code execution, file deletion, or sensitive data disclosure on the underlying host.

Critical Impact
An unauthenticated remote attacker can inject crafted serialized PHP objects to compromise confidentiality, integrity, and availability of affected WordPress sites.

Affected Products

Integration for Contact Form 7 HubSpot WordPress plugin (cf7-hubspot)
All versions <= 1.3.7
WordPress sites with the plugin active and reachable over the network

Discovery Timeline

2026-06-15 - CVE-2026-49763 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2026-49763

Vulnerability Analysis

The plugin passes attacker-controllable input into a PHP deserialization sink without sanitization or type enforcement. PHP Object Injection occurs when unserialize() processes data sourced from HTTP requests, cookies, or stored options under attacker control. The deserialization process triggers PHP magic methods such as __wakeup(), __destruct(), __toString(), and __call() on the reconstructed objects. Adversaries chain these magic methods through classes loaded by WordPress core or third-party plugins to reach dangerous sinks like file I/O, SQL execution, or shell invocation. No authentication is required, and exploitation traverses the network with low complexity and no user interaction.

Root Cause

The root cause is improper deserialization of untrusted input within the cf7-hubspot plugin code path. The plugin invokes unserialize() (or an equivalent unsafe routine) on data that originates from an unauthenticated request channel. PHP autoloading then materializes arbitrary class instances, exposing every magic method in the loaded codebase as a reachable gadget. See the Patchstack Vulnerability Report for the affected code path.

Attack Vector

An attacker crafts a serialized PHP payload containing one or more gadget objects. The payload is delivered to the vulnerable endpoint exposed by the plugin over HTTP or HTTPS. When the plugin deserializes the payload, the constructed object graph executes the chained magic methods. Outcomes include arbitrary code execution, arbitrary file write or delete, authentication bypass through option overwrites, or exfiltration of database secrets. No prior credentials, tokens, or user interaction are required.

No verified public proof-of-concept code is available at the time of writing. Refer to the linked Patchstack advisory for further technical detail.

Detection Methods for CVE-2026-49763

Indicators of Compromise

HTTP request bodies or query parameters containing PHP serialization markers such as O:, a:, or s: directed at cf7-hubspot plugin endpoints
Unexpected child processes spawned by the PHP-FPM or web server user shortly after requests to Contact Form 7 endpoints
New or modified PHP files under wp-content/uploads/ or plugin directories
Outbound network connections from the web host to unfamiliar hosts immediately following form submissions

Detection Strategies

Inspect web server access logs for POST requests targeting Contact Form 7 or HubSpot integration endpoints that contain serialized object signatures
Deploy WAF rules that flag request payloads matching the regex pattern for PHP serialized objects (O:\d+:")
Monitor PHP error logs for __wakeup, __destruct, or class-not-found warnings tied to the plugin
Hunt for anomalous file system writes initiated by the WordPress process after public form submissions

Monitoring Recommendations

Enable file integrity monitoring on the WordPress installation, particularly wp-content/plugins/cf7-hubspot/ and wp-content/uploads/
Forward web server, PHP-FPM, and OS audit logs to a centralized analytics platform for correlation
Alert on first-seen outbound connections from web-tier hosts and on new cron jobs or scheduled tasks created by the web user

How to Mitigate CVE-2026-49763

Immediate Actions Required

Update the Integration for Contact Form 7 HubSpot plugin to a fixed release above 1.3.7 as soon as it is published by the vendor
If no patch is yet available, deactivate and remove the plugin from all WordPress installations
Audit WordPress sites for unauthorized administrator accounts, modified files, and unexpected scheduled tasks
Rotate WordPress secrets in wp-config.php, database credentials, and any API keys stored in the database

Patch Information

Consult the Patchstack Vulnerability Report for the current vendor patch status and the affected versions through 1.3.7. Apply the vendor-supplied update through the WordPress plugin manager or by replacing the plugin directory with the fixed release.

Workarounds

Restrict access to Contact Form 7 endpoints with IP allow-listing or authentication at the reverse proxy layer until patched
Deploy a WAF rule blocking inbound payloads that contain PHP serialization tokens against the affected URIs
Disable the plugin and replace it with an alternative HubSpot integration that does not deserialize untrusted input
Run PHP with disable_functions configured to remove commonly abused sinks used in object injection gadget chains

bash

# Example WAF rule (ModSecurity) blocking PHP serialized payloads to the plugin
SecRule REQUEST_URI "@contains cf7-hubspot" \
    "id:1004976,phase:2,deny,status:403,\
    chain,msg:'CVE-2026-49763 PHP Object Injection attempt'"
    SecRule ARGS|REQUEST_BODY "@rx O:\d+:\"[A-Za-z0-9_\\\\]+\":\d+:" \
        "t:none"