CVE-2025-11226 is a medium severity vulnerability in the QOS.CH Sarl Logback-core Java logging framework, specifically affecting versions up to and including 1.5.18. The vulnerability stems from improper input validation (CWE-20) during conditional configuration file processing. An attacker with existing high privileges and write access to a Logback configuration file can exploit this flaw to execute arbitrary code. Alternatively, an attacker can inject a malicious environment variable before program execution that points to a crafted configuration file, leading to code execution. Successful exploitation requires the presence of both the Janino library and the Spring Framework on the application's classpath. The vulnerability leverages the dynamic evaluation capabilities of Logback's configuration processing, which, when combined with malicious input, allows execution of attacker-controlled code. Exploitation requires prior access to the system with elevated privileges (PR:H) and user interaction (UI:P), limiting the attack surface to scenarios where an attacker already has some level of system access or can influence environment variables before application startup. The vulnerability impacts confidentiality, integrity, and availability due to arbitrary code execution potential. No known exploits are currently reported in the wild. The CVSS 4.0 base score is 5.9 (medium), reflecting the complexity and required privileges for exploitation.

For European organizations, this vulnerability poses a significant risk primarily in environments running Java applications that utilize Logback-core for logging, especially those integrating the Janino library and Spring Framework. Successful exploitation could lead to arbitrary code execution, enabling attackers to compromise application integrity, exfiltrate sensitive data, disrupt services, or establish persistence. Given that Logback is widely used in enterprise Java applications, including financial services, healthcare, and government sectors prevalent in Europe, the impact could be substantial if exploited. However, the requirement for high privileges and write access to configuration files limits the risk to insider threats or attackers who have already breached perimeter defenses. Organizations with complex Java application stacks or those that allow environment variable injection during deployment (e.g., containerized or cloud environments) may face higher exposure. The vulnerability could also be leveraged in supply chain attacks if malicious configuration files are introduced during development or deployment phases. Overall, the threat could lead to data breaches, service outages, and reputational damage for European entities relying on vulnerable Logback-core versions.

1. Upgrade Logback-core to the latest version beyond 1.5.18 where this vulnerability is patched. 2. Restrict write permissions on Logback configuration files to trusted administrators only, preventing unauthorized modification. 3. Harden environment variable management by validating and sanitizing inputs before application startup, especially in containerized or automated deployment pipelines. 4. Remove or restrict the use of the Janino library and Spring Framework if not essential, or ensure they are updated to secure versions. 5. Implement strict application whitelisting and runtime application self-protection (RASP) to detect and block unauthorized code execution attempts. 6. Conduct regular audits of configuration files and environment variables to detect unauthorized changes. 7. Employ least privilege principles for application and system users to reduce the risk of privilege escalation. 8. Monitor logs and system behavior for anomalies indicative of exploitation attempts. These measures go beyond generic patching by focusing on access control, environment hygiene, and runtime protections tailored to the vulnerability's exploitation vectors.