EUVD-2026-37642Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Unauthenticated network-reachable PHP object injection in a WordPress plugin yields RCE-class impact: AV:N, AC:L, PR:N, UI:N, and full C/I/A High.
Primary rating from Vendor (Patchstack).
CVSS VectorVendor: Patchstack
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
1DescriptionCVE.org
Unauthenticated PHP Object Injection in WP Activity Log <= 5.6.3.1 versions.
AnalysisAI
Unauthenticated PHP object injection in the WP Activity Log WordPress plugin versions 5.6.3.1 and earlier allows remote attackers to deliver crafted serialized payloads that are deserialized by the plugin, enabling abuse of any POP (property-oriented programming) gadget chain present in WordPress core, other active plugins, or themes. With a CVSS 3.1 base of 9.8 (AV:N/AC:L/PR:N/UI:N) and no authentication required, successful exploitation typically yields remote code execution, arbitrary file operations, or database compromise on the affected site. No public exploit identified at time of analysis and the vulnerability is not listed in CISA KEV, but the unauthenticated network-reachable nature makes it a high-priority patch for any site running the plugin.
Technical ContextAI
WP Activity Log (CPE cpe:2.3:a:melapress:wp_activity_log) is a widely deployed WordPress audit-logging plugin from Melapress that records administrative and user activity across a WordPress site. The root cause is CWE-502 (Deserialization of Untrusted Data): the plugin passes attacker-controllable input into PHP's unserialize() (or an equivalent deserialization routine) without validating that the serialized stream comes from a trusted source. In PHP, unserialize() reconstructs objects and invokes magic methods such as __wakeup(), __destruct(), and __toString(), which lets an attacker chain methods across loaded classes (POP gadget chains) - a well-known WordPress attack pattern because the core, plugins, and themes expose a large universe of usable gadgets.
RemediationAI
Upstream fix available per the Patchstack advisory; a specific patched release version is not independently confirmed in the input data, so administrators should upgrade WP Activity Log to the latest version newer than 5.6.3.1 published by Melapress and verify the changelog references this PHP object injection fix (advisory: https://patchstack.com/database/wordpress/plugin/wp-security-audit-log/vulnerability/wordpress-wp-activity-log-plugin-5-6-3-1-php-object-injection-vulnerability). If immediate patching is not possible, deactivate and remove the plugin until it can be updated - given it is an auditing plugin, the trade-off is loss of activity logging during the gap. As a compensating control, deploy a WAF rule (Patchstack, Wordfence, or equivalent) that blocks request bodies containing serialized PHP markers such as O:, a:, and s: targeting the plugin's endpoints, accepting that overly broad rules can false-positive on legitimate admin traffic. Restrict access to the plugin's exposed AJAX/REST endpoints by IP allowlist at the web server or reverse proxy layer where feasible.
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Same weakness CWE-502 – Deserialization of Untrusted Data
View allSame technique Deserialization
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External POC / Exploit Code
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