CVE-2025-27636 is a vulnerability in Apache Camel's default incoming header filter mechanism affecting multiple versions (3.10.0 to 3.22.3, 4.8.0 to 4.8.4, and 4.10.0 to 4.10.1). Apache Camel is an integration framework widely used for routing and mediation rules. The vulnerability stems from a bug in the header filtering logic that only blocks headers starting with exact strings "Camel", "camel", or "org.apache.camel.". This filtering is case-sensitive and does not account for variations in casing or other header name manipulations. Attackers can exploit this by injecting crafted headers that bypass the filter, enabling them to manipulate internal Camel headers. For example, in the camel-bean component, an attacker can cause the invocation of unintended methods on beans, potentially altering application logic. In the camel-jms component, malicious headers can redirect messages to unauthorized queues on the same broker. The vulnerability affects numerous Camel components that use the default header filter, including HTTP-based components (camel-servlet, camel-jetty, camel-undertow, camel-platform-http, camel-netty-http), messaging components (camel-activemq, camel-jms, camel-kafka), and others. Exploitation requires the attacker to send HTTP requests with malicious headers to Camel applications exposed to the internet. The vulnerability impacts confidentiality, integrity, and availability by enabling unauthorized method calls and message rerouting. The Apache Software Foundation recommends upgrading to patched versions 4.10.2, 4.8.5, or 3.22.4. As a workaround, users can remove or sanitize headers in Camel routes using the removeHeaders Enterprise Integration Pattern (EIP), filtering out headers with case variations or unexpected prefixes. This vulnerability is tracked as CWE-178 (Improper Neutralization of Input During Web Page Generation). The CVSS v3.1 base score is 5.6 (medium), reflecting network attack vector, high attack complexity, no privileges required, no user interaction, and limited impact on confidentiality, integrity, and availability.

For European organizations, this vulnerability poses a moderate risk especially to enterprises relying on Apache Camel for critical integration workflows, particularly those exposing Camel HTTP components directly to the internet. Exploitation could lead to unauthorized method execution within applications, potentially altering business logic or data processing flows, and message redirection within messaging systems, which could disrupt operations or leak sensitive information. Industries with high integration dependency such as finance, telecommunications, manufacturing, and public sector services could face operational disruptions or data integrity issues. Given the widespread use of Apache Camel in middleware and integration platforms, the vulnerability could affect supply chains and interconnected systems. The moderate CVSS score indicates that while exploitation is not trivial, successful attacks could impact confidentiality, integrity, and availability of services. Organizations failing to patch or implement mitigations risk unauthorized access and manipulation of internal processes, which could cascade into broader security incidents or compliance violations under GDPR if personal data is involved.

1. Upgrade Apache Camel to the fixed versions: 4.10.2 for 4.10.x LTS, 4.8.5 for 4.8.x LTS, or 3.22.4 for 3.x releases as soon as possible. 2. Implement header sanitization in Camel routes by using the removeHeaders EIP to filter out all headers that do not strictly match the allowed prefixes "Camel", "camel", or "org.apache.camel." including case variations (e.g., "cAmel", "cAMEL"). 3. Restrict exposure of Camel HTTP components to the internet; use network-level controls such as firewalls, API gateways, or reverse proxies to limit access. 4. Conduct thorough code reviews and testing to ensure no unintended method invocations can occur via header manipulation. 5. Monitor logs and network traffic for suspicious or malformed headers that could indicate exploitation attempts. 6. Apply strict input validation and implement security controls around messaging components to prevent unauthorized message redirection. 7. Educate developers and operations teams about the risks of header injection and secure integration patterns. 8. Consider deploying Web Application Firewalls (WAFs) with custom rules to detect and block suspicious Camel header injections. 9. Maintain an inventory of all Camel components in use and their exposure levels to prioritize patching and mitigation efforts.