CVE-2025-29457 is a high-severity vulnerability affecting MyBB forum software version 1.8.38. The issue arises from the 'Import a Theme' functionality, which allows a remote attacker with board administrator privileges to potentially obtain sensitive information. The vulnerability is categorized under CWE-918, which corresponds to Server-Side Request Forgery (SSRF). SSRF vulnerabilities enable attackers to induce the server to make HTTP requests to arbitrary domains, potentially exposing internal resources or sensitive data. In this case, the attacker leverages the theme import feature to trigger SSRF-like behavior, which could lead to unauthorized disclosure of sensitive information. However, the supplier disputes the severity or exploitability of this vulnerability, citing the requirement that only board administrators can perform the import action and that SSRF mitigations are in place. The CVSS v3.1 score is 7.6 (high), reflecting a network attack vector with low attack complexity, requiring privileges (PR:L), no user interaction, and impacting confidentiality (high), integrity (low), and availability (low). No known exploits are currently in the wild, and no patches have been linked yet. The vulnerability was reserved in March 2025 and published in April 2025. Given the nature of the vulnerability, exploitation requires authenticated access with elevated privileges, limiting the attack surface to insiders or compromised administrator accounts. Nonetheless, successful exploitation could lead to significant information disclosure, which could facilitate further attacks or data breaches within affected MyBB installations.

For European organizations using MyBB 1.8.38 as their forum or community platform, this vulnerability poses a significant risk primarily due to the potential exposure of sensitive internal information via SSRF. Although exploitation requires board administrator privileges, many organizations may have multiple administrators or insufficiently protected admin accounts, increasing the risk of compromise. Information disclosure could lead to leakage of internal network details, configuration files, or other sensitive data, which attackers could leverage for lateral movement or targeted attacks. This is particularly impactful for organizations in sectors with stringent data protection requirements such as finance, healthcare, and government agencies. The availability impact is low, so service disruption is unlikely, but the confidentiality breach could result in regulatory penalties under GDPR if personal data is exposed. The integrity impact is low, meaning data modification is not the primary concern. Since no public exploits are known yet, the immediate threat is moderate, but the presence of a high CVSS score indicates that organizations should act promptly to mitigate risk. The dispute by the supplier suggests that organizations should carefully evaluate their administrative access controls and SSRF mitigations to assess their exposure.

Restrict 'Import a Theme' functionality strictly to the minimum number of trusted board administrators and enforce strong authentication mechanisms such as multi-factor authentication (MFA) for all admin accounts. Conduct a thorough audit of all board administrator accounts to ensure no unauthorized or stale accounts exist. Implement network segmentation and firewall rules to limit the MyBB server's ability to make outbound HTTP requests to untrusted or internal network resources, thereby reducing SSRF impact. Monitor and log all theme import activities and related administrative actions to detect suspicious behavior promptly. Apply principle of least privilege on the MyBB server and underlying infrastructure to minimize potential damage from exploitation. Since no official patch is currently available, consider disabling the 'Import a Theme' feature temporarily if feasible until a vendor patch or update is released. Review and enhance existing SSRF mitigations, including validating and sanitizing URLs or inputs used in the theme import process. Keep abreast of vendor advisories and apply patches immediately once released.