CVE-2025-26999 Overview
CVE-2025-26999 is a PHP Object Injection vulnerability in the Metagauss ProfileGrid WordPress plugin (profilegrid-user-profiles-groups-and-communities). The flaw stems from deserialization of untrusted data [CWE-502] and affects all versions up to and including 5.9.4.3. An authenticated attacker with low privileges can submit crafted serialized payloads that the plugin unsafely deserializes, instantiating arbitrary PHP objects within the application context. When combined with a suitable POP (Property-Oriented Programming) gadget chain in WordPress core or other installed plugins, the issue can escalate to remote code execution, data tampering, or full site compromise.
Critical Impact
Authenticated attackers can trigger object injection to compromise confidentiality, integrity, and availability of WordPress sites running ProfileGrid <= 5.9.4.3.
Affected Products
- Metagauss ProfileGrid (profilegrid-user-profiles-groups-and-communities) WordPress plugin
- All versions from n/a through 5.9.4.3
- WordPress installations exposing ProfileGrid user, group, and community features
Discovery Timeline
- 2025-03-03 - CVE-2025-26999 published to NVD
- 2026-04-23 - Last updated in NVD database
Technical Details for CVE-2025-26999
Vulnerability Analysis
The vulnerability is categorized under [CWE-502]: Deserialization of Untrusted Data. ProfileGrid passes attacker-controlled input into PHP's unserialize() function without validating the source or structure of the serialized blob. PHP deserialization in this context invokes magic methods such as __wakeup(), __destruct(), and __toString() on instantiated objects. If any class loaded in the WordPress runtime exposes a usable gadget chain, an attacker can pivot from object injection to file writes, SQL execution, or arbitrary code execution. The issue is reachable over the network and requires only low-privilege authentication, which is commonly available on sites that allow user self-registration through ProfileGrid itself.
Root Cause
The root cause is the use of unsafe deserialization on input that crosses a trust boundary. The plugin treats serialized data submitted through plugin endpoints as trusted and processes it directly with unserialize() rather than using safe formats such as JSON or applying the allowed_classes option introduced in PHP 7. Without a class allowlist, every loaded class becomes a potential gadget.
Attack Vector
Exploitation requires network access to the WordPress site and an authenticated session with at least subscriber-level capabilities. The attacker submits a serialized PHP object string to a ProfileGrid endpoint that processes user-controlled data. Upon deserialization, the chosen gadget chain executes during object lifecycle hooks. Refer to the Patchstack Vulnerability Report for additional technical context.
Detection Methods for CVE-2025-26999
Indicators of Compromise
- HTTP requests to ProfileGrid AJAX or REST endpoints containing serialized PHP markers such as O:, a:, or s: in parameter values.
- Unexpected PHP errors referencing __wakeup, __destruct, or unserialize() in WordPress debug logs.
- New or modified files under wp-content/uploads/ or wp-content/plugins/ that do not correspond to legitimate administrative activity.
- Creation of unexpected administrator accounts or modification of the wp_options table following plugin requests.
Detection Strategies
- Inspect web server and PHP-FPM logs for POST bodies containing serialized object patterns directed at ProfileGrid endpoints.
- Deploy WAF signatures that flag PHP serialized object markers in request parameters bound for the plugin.
- Correlate authenticated low-privilege user activity with subsequent privileged actions such as user role changes or option updates.
- Hash and baseline plugin files to detect post-exploitation tampering.
Monitoring Recommendations
- Enable WordPress audit logging for user role, capability, and option changes.
- Forward web server, PHP, and WordPress logs to a central analytics platform for retention and correlation.
- Alert on outbound connections from the PHP worker process to unexpected destinations, which can indicate post-exploitation callbacks.
How to Mitigate CVE-2025-26999
Immediate Actions Required
- Update the ProfileGrid plugin to a release later than 5.9.4.3 as soon as the vendor publishes a fixed version.
- Audit existing WordPress user accounts and revoke any unexpected administrator or editor privileges.
- Rotate WordPress secret keys in wp-config.php and force password resets for privileged users.
- Review installed plugins and themes for known POP gadget chains and remove unused components.
Patch Information
Consult the Patchstack Vulnerability Report for the authoritative fixed-version reference and apply the patched release through the WordPress plugin manager or WP-CLI using wp plugin update profilegrid-user-profiles-groups-and-communities.
Workarounds
- Temporarily deactivate the ProfileGrid plugin until a patched version is installed.
- Restrict access to ProfileGrid endpoints with a web application firewall rule that blocks serialized PHP payloads.
- Disable open user registration to reduce the population of low-privilege accounts capable of reaching vulnerable endpoints.
# Example WP-CLI mitigation commands
wp plugin deactivate profilegrid-user-profiles-groups-and-communities
wp plugin update profilegrid-user-profiles-groups-and-communities
wp user list --role=administrator --fields=ID,user_login,user_email,user_registered
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
