CVE-2025-47784 is a medium-severity vulnerability affecting emlog, an open-source website building system, specifically versions 2.5.13 and earlier. The vulnerability is categorized under CWE-502, which pertains to the deserialization of untrusted data. In this case, an attacker can exploit the way emlog handles user input, particularly a crafted nickname. The vulnerability arises because the function str_replace is used to manipulate the value of name_orig during deserialization. By creating a carefully crafted nickname, an attacker can cause str_replace to replace the value of name_orig with an empty string, causing the deserialization process to fail and return false. This failure in deserialization can lead to unexpected behavior, potentially allowing an attacker to disrupt application logic or cause denial of service. The vulnerability does not require authentication or user interaction, and the attack vector is network-based, meaning it can be exploited remotely without privileges. The CVSS 4.0 base score is 6.6, indicating a medium severity level. The vulnerability was fixed in a commit identified as 9643250802188b791419e3c2188577073256a8a2. There are no known exploits in the wild at the time of publication. The vulnerability impacts the integrity and availability of the affected system, as improper deserialization can lead to application errors or crashes. The scope is limited to emlog versions up to 2.5.13, and the attack does not require any user interaction or authentication, increasing the risk of exploitation. However, the absence of known exploits and the medium CVSS score suggest that the vulnerability is moderate in risk but should be addressed promptly.

For European organizations using emlog as their website building platform, this vulnerability poses a risk primarily to the integrity and availability of their web applications. Exploitation could lead to application failures or denial of service, disrupting online services and potentially damaging reputation and customer trust. Since emlog is open source and may be used by small to medium enterprises or niche websites, the impact could be significant for organizations relying on it for their public-facing websites. The vulnerability could also be leveraged as part of a larger attack chain, especially if combined with other vulnerabilities or misconfigurations. Given that no authentication is required, attackers can attempt exploitation remotely, increasing the threat surface. Organizations in sectors with high web presence, such as e-commerce, media, and public services, could face operational disruptions. Additionally, the failure in deserialization might be used to bypass certain application logic or security controls, potentially leading to further compromise if combined with other vulnerabilities. The lack of known exploits currently reduces immediate risk but does not eliminate the need for mitigation.

European organizations should immediately upgrade emlog installations to versions later than 2.5.13 where the issue is fixed by the referenced commit. If upgrading is not immediately feasible, organizations should implement input validation and sanitization on user-supplied nicknames to prevent malicious payloads from triggering the vulnerability. Web application firewalls (WAFs) can be configured to detect and block suspicious payloads targeting deserialization routines. Monitoring logs for unusual deserialization failures or application errors related to nickname processing can help detect attempted exploitation. Additionally, organizations should conduct a thorough review of their emlog configurations and restrict access to administrative interfaces to trusted networks. Regular security assessments and penetration testing focusing on deserialization vulnerabilities can help identify residual risks. Finally, maintaining an incident response plan that includes scenarios involving deserialization attacks will improve readiness.