CVE-2026-57371 Overview
CVE-2026-57371 is a PHP Object Injection vulnerability in the WPJAM Basic WordPress plugin developed by denishua. The flaw stems from insecure deserialization of untrusted data [CWE-502] and affects all plugin versions up to and including 7.0. Authenticated attackers with low privileges can supply crafted serialized payloads that instantiate arbitrary PHP objects during deserialization. When paired with a suitable gadget chain in the WordPress environment, the issue can lead to remote code execution, data tampering, or full site compromise.
Critical Impact
Authenticated attackers can inject arbitrary PHP objects into the WPJAM Basic plugin, enabling potential remote code execution and complete compromise of WordPress site confidentiality, integrity, and availability.
Affected Products
- WPJAM Basic WordPress plugin (wpjam-basic)
- All versions from n/a through 7.0
- Vendor: denishua
Discovery Timeline
- 2026-07-13 - CVE-2026-57371 published to NVD
- 2026-07-13 - Last updated in NVD database
Technical Details for CVE-2026-57371
Vulnerability Analysis
The vulnerability is an Insecure Deserialization flaw classified under [CWE-502]. The WPJAM Basic plugin passes attacker-controllable input to a PHP deserialization function such as unserialize() without validating the source or content of the serialized data. During deserialization, PHP reconstructs objects and automatically invokes magic methods including __wakeup(), __destruct(), and __toString() on those objects.
Attackers exploit this behavior by crafting serialized payloads that reference existing classes loaded in the WordPress runtime. Chained gadgets across WordPress core, other installed plugins, or theme code can then be triggered to perform file operations, execute SQL queries, or achieve arbitrary code execution. The attacker requires low-privilege authentication, which lowers the exploitation barrier on sites with open registration or weak account controls.
Root Cause
The root cause is the direct deserialization of user-supplied input inside WPJAM Basic without prior integrity checks or safe list controls. PHP's native unserialize() treats serialized strings as trusted structural data, so any influence over the input allows an attacker to control object type, properties, and lifecycle callbacks.
Attack Vector
Exploitation occurs over the network against the WordPress site. The attacker submits a crafted serialized string through a plugin request handler exposed to authenticated users. Because the flaw is reachable with only low privileges, contributor-level or subscriber-level accounts may be sufficient depending on the endpoint. No user interaction from an administrator is required.
No verified public proof-of-concept code is available. Refer to the Patchstack Vulnerability Report for technical details.
Detection Methods for CVE-2026-57371
Indicators of Compromise
- Unexpected serialized PHP strings beginning with O:, a:, or s: in HTTP POST bodies, cookies, or query parameters targeting WPJAM Basic endpoints.
- Creation of unfamiliar PHP files under wp-content/uploads/ or plugin directories following authenticated requests.
- Unexplained outbound network connections or scheduled tasks originating from the www-data process running WordPress.
Detection Strategies
- Inspect web server access logs for requests to wpjam-basic endpoints containing URL-encoded serialized object markers such as O%3A or a%3A.
- Monitor WordPress database options and postmeta tables for serialized payloads that reference unexpected class names.
- Correlate low-privilege user activity with subsequent file writes or PHP process spawns on the host.
Monitoring Recommendations
- Enable audit logging for authentication events and plugin request handlers on the WordPress site.
- Alert on PHP unserialize errors and warnings in application logs, which often accompany failed object injection attempts.
- Track integrity of plugin files, WordPress core files, and the wp-config.php file to identify tampering.
How to Mitigate CVE-2026-57371
Immediate Actions Required
- Disable or uninstall the WPJAM Basic plugin until a patched version above 7.0 is released and verified.
- Audit existing WordPress user accounts and revoke unnecessary low-privilege access that could be leveraged for exploitation.
- Rotate WordPress secret keys, administrator passwords, and database credentials if compromise is suspected.
Patch Information
At the time of publication, no fixed version above WPJAM Basic 7.0 is documented in the referenced advisory. Site operators should monitor the Patchstack Vulnerability Report and the vendor's plugin page for an updated release addressing the deserialization flaw.
Workarounds
- Restrict access to WPJAM Basic administrative endpoints using web application firewall rules that block serialized object patterns in request parameters.
- Enforce strong authentication and multi-factor authentication on all WordPress accounts to reduce the pool of usable low-privilege credentials.
- Deploy a virtual patch through Patchstack or an equivalent WordPress security service until an official fix is available.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
