CVE-2025-11226 is an improper input validation vulnerability (CWE-20) in the Logback-core library developed by QOS.CH Sarl, affecting versions up to and including 1.5.18. Logback-core is a widely used Java logging framework component. The vulnerability arises from insecure processing of conditional configuration files, which can be manipulated by an attacker to execute arbitrary code. Specifically, if an attacker has write access to an existing logback configuration file or can inject a malicious environment variable that points to a crafted configuration file, they can trigger code execution. This attack requires the presence of the Janino library, a runtime Java compiler, and the Spring Framework on the application's classpath, which are common in enterprise Java applications. The attacker must already have high privileges (e.g., administrative or system-level access) to modify configuration files or environment variables before the application starts. The vulnerability is exploitable locally with low attack complexity but requires user interaction and existing privileges, limiting remote exploitation. The CVSS v4.0 score is 5.9 (medium severity), reflecting the need for high privileges and user interaction but the potential for significant impact on confidentiality, integrity, and availability. No public exploits have been reported to date. The vulnerability highlights risks in configuration file handling and environment variable injection in Java applications relying on Logback-core, especially when combined with Janino and Spring Framework.

For European organizations, this vulnerability poses a risk primarily to Java-based enterprise applications that utilize Logback-core for logging and include the Janino library and Spring Framework. Successful exploitation could lead to arbitrary code execution, compromising application confidentiality, integrity, and availability. This could enable attackers to escalate privileges, move laterally within networks, or disrupt critical business services. Organizations in sectors with high reliance on Java applications, such as finance, manufacturing, telecommunications, and government, may face operational disruptions and data breaches. The requirement for existing high privileges and write access limits the scope but does not eliminate risk, especially in environments where insider threats or compromised accounts exist. Additionally, injection via environment variables before program execution could be leveraged in containerized or cloud environments where environment variables are commonly used, increasing the attack surface. The absence of known exploits provides a window for proactive mitigation, but organizations should act promptly to prevent potential exploitation.

To mitigate CVE-2025-11226, European organizations should implement the following specific measures: 1) Restrict write permissions on logback configuration files to trusted administrators only, preventing unauthorized modification. 2) Harden environment variable management, especially in containerized and cloud environments, by validating and sanitizing environment inputs and limiting injection capabilities. 3) Audit Java application dependencies to identify the presence of Logback-core versions up to 1.5.18, Janino library, and Spring Framework, and plan for upgrades or patches once available. 4) Employ runtime application self-protection (RASP) or endpoint detection and response (EDR) solutions to monitor for suspicious configuration file changes or environment variable manipulations. 5) Enforce the principle of least privilege to reduce the number of users and processes with write access to configuration files and environment variables. 6) Conduct regular security reviews and penetration tests focusing on configuration file integrity and environment variable injection vectors. 7) Monitor logs for unusual application behavior or errors related to logging configuration parsing. 8) Prepare incident response plans to quickly address any signs of exploitation. These targeted steps go beyond generic advice by focusing on configuration file security and environment variable hygiene in Java application contexts.