julienbrs/exploit-cve-2023-3460Exploit and analysis of CVE-2023-3460, a critical privilege escalation in the Ultimate Member WordPress plugin, with reproduction environment and mitigation guidance.
| CVE ID | CVSS Score | Discovered | Affected Plugin | Vulnerability Type |
|---|---|---|---|---|
| CVE-2023-3460 |  | 07/04/2023 | Ultimate Member | Unauthorized Admin Access |
This study focuses on CVE¹-2023-3460, a critical vulnerability affecting the "Ultimate Member" WordPress plugin, allowing unauthorized privilege escalation. This plugin is widely deployed and used for profile management on WordPress sites. This vulnerability poses a major risk because it allows an attacker to obtain administrator rights and therefore full control of the site. This is why this flaw was classified as critical and rated 9.1 on the CVSS scale by NIST².
CVE-2023-3460 exploits a flaw in the plugin's role and permission management. In WordPress, the WP_Capabilities³ function is used to manage user roles and permissions. This function allows administrators to define specific capabilities for each user role. However, improper use of this function can lead to privilege escalation vulnerabilities.
In the case of Ultimate Member, the vulnerability allows an attacker to bypass WP capability checks and gain administrator-level access to the site. The plugin operates by using a predefined list of user metadata keys that should not be manipulated by users. However, this security approach, based on blocklists, is often insufficient because it leaves room for bypasses.
WordPress manages user roles and permissions through a structure called wp_capabilities. This structure is a serialized representation of the different roles and permissions granted to users. For example, an administrator will have a different set of capabilities than an editor or a contributor. These capabilities are stored in the WordPress database as serialized arrays in the wp_usermeta table.
The CVE-2023-3460 flaw originates from Ultimate Member's implementation of role and permission management. The plugin operates by using a predefined list of user metadata keys that users should not manipulate. This list is used to check whether users attempt to save these keys when creating an account. This approach is a common security anti-pattern, where blocking known harmful inputs (blocklists) may seem intuitive, but proves more complex than expected and often leaves room for security bypasses.
Here, Ultimate Member uses insufficient verification of metadata submitted during user registration. The plugin uses a function called is_metakey_banned to check whether the metadata submitted by the user is allowed. This function checks whether the submitted metadata appears in the list of banned metadata. If so, the function returns true and user registration is blocked. Otherwise, the function returns false and user registration is allowed.
However, WordPress accepts certain accented characters as default characters. If a user submits metadata with accented characters, the is_metakey_banned function will not detect them and user registration will be allowed.
The Ultimate Member plugin is widely used in various environments, ranging from small personal blogs to large e-commerce sites. No specific assumption can be made about the IT security skills of end users or site administrators.
Servers hosting WordPress sites are generally located in secure data centers. For personal sites, physical security depends on the individual user's environment.
It is assumed that the Ultimate Member plugin is installed and configured correctly according to the official instructions. The WordPress site is assumed to be kept up to date, with basic security measures in place.
| Threats | A1 (User data confidentiality) | A2 (Website integrity) | A3 (Ultimate Member plugin integrity) |
|---|---|---|---|
| T1 Unauthorized access | X | X | X |
| T2 Malicious code injection | X | X | |
| T3 Data leakage | X | ||
| T4 Reputation damage | X |
7.5 Security functions
