CVE-2025-54813 is a medium severity vulnerability classified under CWE-117 (Improper Output Neutralization for Logs) affecting the Apache Software Foundation's Apache Log4cxx library, specifically versions prior to 1.5.0. The vulnerability arises when using the JSONLayout feature of Log4cxx, where not all payload bytes, particularly certain non-printable characters supplied by an attacker, are properly escaped before being logged. This improper neutralization allows these characters to be written directly into the JSON-formatted log messages. As a result, applications or systems that consume and parse these logs may misinterpret the log data, potentially leading to incorrect processing, log injection, or log forging scenarios. Although this vulnerability does not directly allow remote code execution or privilege escalation, it undermines the integrity and reliability of log data, which is critical for forensic analysis, monitoring, and incident response. The vulnerability requires no authentication or user interaction and can be exploited remotely by sending crafted log messages that include malicious payloads with non-printable characters. The Apache Log4cxx library is a C++ port of the widely used Java-based Log4j logging framework, and it is commonly embedded in various enterprise and industrial applications for logging purposes. The vendor has addressed this issue in version 1.5.0 by ensuring proper escaping of all payload bytes in JSONLayout, mitigating the risk of log misinterpretation.

For European organizations, the impact of this vulnerability primarily affects the integrity and reliability of logging systems that utilize Apache Log4cxx with JSONLayout enabled. Since logs are essential for security monitoring, compliance auditing, and incident investigations, corrupted or misinterpreted logs can hinder the detection of malicious activities and delay response efforts. This can lead to prolonged dwell time for attackers and increased risk of data breaches or operational disruptions. Industries with stringent regulatory requirements such as finance, healthcare, and critical infrastructure in Europe may face compliance challenges if logs are compromised. Additionally, organizations relying on automated log analysis tools may experience false negatives or positives, reducing the effectiveness of security operations centers (SOCs). While the vulnerability does not directly compromise confidentiality or availability, the degradation of log integrity can indirectly facilitate more severe attacks by obscuring attacker actions. Given the widespread use of Apache logging frameworks in European software stacks, especially in legacy or embedded systems, the vulnerability poses a moderate risk that should be addressed promptly.

European organizations should prioritize upgrading Apache Log4cxx to version 1.5.0 or later, where the vulnerability is fixed. For environments where immediate upgrade is not feasible, organizations should implement strict input validation and sanitization on all data that may be logged, especially if it originates from untrusted sources. Additionally, consider disabling JSONLayout if it is not required or replacing it with alternative logging formats that properly escape non-printable characters. Implement monitoring to detect anomalous log entries containing suspicious non-printable or control characters that could indicate exploitation attempts. Security teams should also review and harden log ingestion and parsing pipelines to handle malformed logs gracefully without misinterpretation. Finally, incorporate this vulnerability into vulnerability management and patching workflows to ensure timely remediation and verification of fixes across all affected systems.