CVE-2026-73099 in Juneau
Summary
by MITRE • 11/05/2026
Cross-Site Request Forgery (CSRF) vulnerability in Apache Juneau.
The REST server accepts a "content" query parameter that replaces the request body, and this is enabled by default on every HTTP method, including GET. A cross-site link can therefore deliver an attacker-chosen request body to an endpoint without a CORS preflight, defeating protections that rely on the HTTP method or content type instead of an anti-CSRF token.
This issue affects Apache Juneau: through 9.2.0.
Users are recommended to upgrade to version 9.2.1, which fixes the issue. Applications that do not use the content parameter can also set disableContentParam to true.
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Analysis
by VulDB Data Team • 11/05/2026
The vulnerability identified in Apache Juneau represents a significant Cross-Site Request Forgery (CSRF) flaw rooted in how the REST server handles HTTP request bodies through query parameters. Specifically, the framework accepts a "content" query parameter that effectively replaces the standard HTTP request body with data provided via the URL. This behavior is enabled by default for all supported HTTP methods, including GET requests which traditionally do not carry a message body. By allowing an attacker to inject arbitrary content into what should be a read-only operation or a simple state-changing action without requiring complex headers, the framework bypasses standard browser security mechanisms that rely on same-origin policies and CORS preflight checks. This design choice creates a scenario where malicious actors can craft links or scripts in external contexts that trigger unintended actions within an authenticated session of Apache Juneau-based applications.
From a technical perspective, this flaw aligns with CWE-352, which describes Cross-Site Request Forgery as the submission of unwanted commands from users whom the web application trusts. The specific mechanism here exploits the fact that many CSRF defenses are built around preventing cross-origin requests that carry sensitive headers or use methods like POST with complex content types. However, because this vulnerability allows body data to be passed via a simple GET request parameter, it circumvents protections that check for Content-Type headers such as application/json or multipart/form-data. An attacker can simply embed an image tag or a script source pointing to the vulnerable endpoint with the malicious payload in the query string, causing the victim's browser to send the forged request without triggering any preflight checks or requiring user interaction beyond clicking a link or loading a page.
The operational impact of this vulnerability is severe for applications relying on Apache Juneau for their REST API implementation. Since the issue affects versions through 9.2.0 and defaults are configured to allow this behavior, most out-of-the-box deployments are susceptible unless explicitly hardened. Attackers can exploit this to perform state-changing operations such as modifying user profiles, executing administrative commands, or transferring funds if financial transactions are involved. The lack of requirement for an anti-CSRF token in these specific request patterns means that traditional CSRF mitigation strategies like double-submit cookies may fail if the application logic does not strictly validate the source and intent of every incoming parameter. This undermines the integrity of user sessions and can lead to unauthorized data manipulation or complete system compromise depending on the privileges associated with the targeted endpoints.
To mitigate this risk, organizations should immediately upgrade Apache Juneau to version 9.2.1 or later, where the default behavior has been corrected to prevent this abuse vector. For applications that cannot upgrade due to legacy constraints or specific architectural requirements, a critical workaround is available by setting the disableContentParam configuration option to true. This action disables the ability of query parameters to replace request bodies, thereby restoring standard HTTP semantics and preventing attackers from injecting payloads via URL strings. Additionally, developers should implement robust CSRF protection mechanisms such as synchronizer tokens for all state-changing operations, regardless of whether they use GET or POST methods, ensuring that every sensitive transaction requires explicit user consent validated by a unique token generated per session. This layered approach ensures resilience against both this specific implementation flaw and broader CSRF attack patterns documented in the MITRE ATT&CK framework under techniques related to browser-based credential theft and request forgery.