CVE-2025-54813 in Log4cxx
Summary
by MITRE • 08/22/2025
Improper Output Neutralization for Logs vulnerability in Apache Log4cxx.
When using JSONLayout, not all payload bytes are properly escaped. If an attacker-supplied message contains certain non-printable characters, these will be passed along in the message and written out as part of the JSON message. This may prevent applications that consume these logs from correctly interpreting the information within them.
This issue affects Apache Log4cxx: before 1.5.0.
Users are recommended to upgrade to version 1.5.0, which fixes the issue.
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Analysis
by VulDB Data Team • 11/03/2025
The CVE-2025-54813 vulnerability represents a critical improper output neutralization for logs issue within Apache Log4cxx library, specifically impacting the JSONLayout functionality. This vulnerability stems from inadequate handling of special characters during log message processing, creating a pathway for malicious actors to inject problematic byte sequences that bypass normal sanitization mechanisms. The flaw manifests when applications utilize JSONLayout to format log output, where certain non-printable characters contained within attacker-controlled messages are not properly escaped or neutralized before being written to log files. This technical deficiency directly violates fundamental security principles for output handling and log management, as it allows potentially harmful data to persist in log structures that are typically expected to be safe and parseable.
The operational impact of this vulnerability extends beyond simple logging complications, as it creates potential for log parsing failures and data corruption within systems that consume these malformed log entries. When applications attempt to process or analyze logs containing unescaped characters, the presence of these non-printable bytes can cause parsing errors, application crashes, or incorrect data interpretation that may obscure legitimate security events or create false positives in security monitoring systems. This vulnerability particularly affects environments where log data feeds into security information and event management systems, intrusion detection systems, or automated log analysis tools that rely on properly formatted JSON structures for their operations. The issue creates a persistent risk for organizations that depend on accurate log data for security operations, forensic analysis, and compliance reporting.
This vulnerability aligns with CWE-117, which specifically addresses improper output neutralization for logs, and demonstrates characteristics consistent with ATT&CK technique T1562.006 related to "Impair Logs and Monitoring" by potentially corrupting log data integrity. The flaw represents a classic example of insufficient input validation and sanitization in logging components, where the assumption that all log data will be properly formatted leads to security weaknesses. Organizations utilizing Apache Log4cxx versions prior to 1.5.0 face significant risk of log data corruption that could mask actual security incidents or create operational disruptions in security monitoring workflows. The remediation approach requires immediate upgrading to version 1.5.0, which implements proper escaping mechanisms for all payload bytes within JSONLayout output, ensuring that non-printable characters are correctly encoded to prevent parsing issues. This fix addresses the root cause by establishing robust output neutralization procedures that align with industry best practices for secure logging implementations and maintain the integrity of log data throughout the security operations lifecycle.