CVE-2026-7761: Ultimate Member Plugin Account Takeover via Password Reset Link Disclosure

Technical summary

CVE-2026-7761 is a privilege escalation vulnerability in Ultimate Member versions up to 2.11.4 exploited through a three-stage attack chain: First, the get_directory_by_hash() function contains a hash fallback that treats MD5(post_id) as a valid member directory identifier, allowing any post to masquerade as a directory by matching SUBSTRING(MD5(post_id), 11, 5). Second, post_data() uses strstr() to validate meta key restrictions, which checks whether '_um_' appears anywhere in the key name rather than requiring it at the start, allowing meta keys like 'custom_um_field' to bypass protected field restrictions. Third, build_user_card_data() fails to validate field names before passing them to um_filtered_value(), permitting arbitrary fields including 'password_reset_link' to be injected into the tagline_fields configuration. An authenticated contributor can exploit all three flaws in sequence: create a malicious post via XMLRPC with crafted meta, point the directory AJAX handler to that post using the MD5 collision, inject password_reset_link into the configuration, and retrieve live reset tokens for all users in the directory response.

Business impact

This vulnerability directly enables account takeover of administrative and other user accounts without requiring knowledge of existing passwords. The attack surface is broad—any user with contributor privileges (authors, editors, and above) can launch the exploit, and the exposure is silent; administrators will not receive notifications that reset links have been leaked. A compromised admin account provides full site control, enabling malware injection, data theft, user account compromise, and ransomware deployment. For multi-site installations, the attack can spread laterally across networks. The disclosure of reset links also creates a time-window risk: even if the initial attacker is detected and removed, any leaked links remain valid for the standard reset window, exposing the site to secondary compromise.

Affected systems

All installations of the Ultimate Member plugin version 2.11.4 and earlier are affected. The plugin is widely used for community-driven WordPress sites, membership directories, user profiles, and community networks. WordPress sites with multi-user environments where contributors or higher-privilege users exist are at immediate risk. The vulnerability requires only network access and a valid user account at contributor level or above—no special network position or advanced capabilities are required.

Exploitability

The attack is highly exploitable. It requires only an authenticated account (contributor level minimum), standard WordPress XMLRPC interface access, and the ability to craft HTTP requests—no zero-day exploit code or complex execution environment needed. The three logic flaws are chained in a straightforward manner: post creation, hash manipulation, and parameter injection. The barrier to exploitation is authentication and contributor privilege, which are common in WordPress sites with editorial teams, guest authors, or community contributors. Once the password reset link is obtained, standard password reset functionality completes the account takeover.

Remediation

Update the Ultimate Member plugin to the patched version (verify current version number against the official Ultimate Member security advisory, as the provided data does not specify the remediated version). The patch should address all three logic flaws: implementing cryptographically sound directory identification instead of MD5 fallback, validating that '_um_' appears at the start of meta keys rather than anywhere in the string, and implementing strict field name whitelisting in build_user_card_data(). Additionally, temporarily disable XMLRPC if it is not required for your workflow, as this limits the attack vector for unauthenticated or lower-privilege user creation.

Patch guidance

Immediately update the Ultimate Member plugin through the WordPress admin dashboard or directly from the official repository. Verify the update version against the official Ultimate Member security advisory published by the vendor. If automatic updates are disabled, manually download and install the patched version. After patching, verify no unauthorized posts exist in the database by reviewing posts created by unexpected users around the publication date of this CVE (June 24–25, 2026). Test that password reset functionality works correctly post-patch. If your site runs on a staging environment, patch there first and verify functionality before deploying to production.

Detection guidance

Search for suspicious post creations via XMLRPC near the vulnerability publication date (June 24–25, 2026 onwards) by reviewing WordPress logs and database queries. Check the wp_postmeta table for meta keys containing '_um_' (not just starting with it) that were added by contributor-level or lower accounts—legitimate use of Ultimate Member fields should follow the plugin's documented naming conventions. Monitor for unusual calls to the member directory AJAX endpoint (typically wp-admin/admin-ajax.php?action=um_directory) with non-standard post_id or hash parameters. Review password reset request logs for clusters of resets initiated from unusual IP addresses or within short timeframes. Check administrative account login history for successful logins from unexpected geographic locations or times following the plugin deployment period.

Why prioritize this

This vulnerability scores 8.8 (HIGH) under CVSS 3.1 due to high impact (confidentiality, integrity, and availability), low attack complexity, and low privilege requirements. The disclosure of password reset links directly enables complete account compromise without requiring password guessing or social engineering. For any WordPress site with contributors or above, this represents a critical path to administrative account takeover. The chained nature of the flaw—requiring exploitation of three separate logic bugs—means no single mitigation (e.g., disabling XMLRPC alone) fully addresses the risk. Immediate patching is strongly recommended for all affected installations.

Risk score, explained

CVSS 3.1 Score: 8.8 (HIGH). Attack Vector: Network (AV:N)—the vulnerability is exploitable over the network without requiring local access. Attack Complexity: Low (AC:L)—no complex exploitation steps or conditions beyond having a valid account. Privileges Required: Low (PR:L)—contributor-level access is sufficient. User Interaction: None (UI:N)—the attack is fully automated once the account is compromised. Scope: Unchanged (S:U)—impact is confined to the affected WordPress installation. Confidentiality Impact: High (C:H)—password reset links expose the ability to reset any account, including admins. Integrity Impact: High (I:H)—successful account takeover allows arbitrary content modification, user creation, and site configuration changes. Availability Impact: High (A:H)—a compromised admin account can disable services, delete content, or shut down the site. The combination of all three 'high' impacts with low barriers to exploitation justifies the HIGH severity classification.

Frequently asked questions