CVE-2026-121489

Allocation of Resources Without Limits or Throttling vulnerability in Apache Juneau. The MessagePack parser, which the REST server enables by default, sizes buffers from length values in the input. An unauthenticated client can send a few bytes that force a multi-gigabyte allocation and an OutOfMemoryError, causing denial of service. Related unbounded allocations in REST request handling (multipart uploads and request reader buffers) are fixed at the same time. This issue affects Apache Juneau: through 9.2.0.

Cross-site Scripting (XSS) vulnerability in Apache Juneau. HTML document serialization does not HTML-encode variable substitutions in page chrome fields (header, nav, footer, etc.), so applications that place request-derived values there reflect them unencoded.

HTTP Response Splitting (CRLF injection in HTTP headers) vulnerability in Apache Juneau. The REST server passed response header values and redirect targets to the servlet container unchecked, so request-derived data could allow header injection or redirect to an arbitrary site.

Insufficiently Protected Credentials vulnerability in Apache Juneau. The RestClient followed HTTP redirects while keeping credential headers from the original request, so a server redirecting to a different host, port, or from HTTPS to HTTP could receive Authorization, Cookie, Proxy-Authorization and X-API-Key headers.

Generation of Error Message Containing Sensitive Information vulnerability in Apache Juneau. The REST server sends the internal exception class and message to clients in a "Thrown" response header on every error response and may include internal exception messages in the error body, even with stack-trace rendering disabled.

Insertion of Sensitive Information into Log File vulnerability in Apache Juneau. The default REST server call logger records request headers for requests ending in a server error without redaction, so Authorization, Cookie, Proxy-Authorization and X-API-Key headers are written in cleartext to the application log.

Cross-Site Request Forgery (CSRF) vulnerability in Apache Juneau. The REST server accepts a "content" query parameter that replaces the request body and is enabled by default on every HTTP method including GET, so a cross-site link can deliver an attacker-chosen request body without a CORS preflight.

Improper control of dynamically-loaded code vulnerability in Apache Juneau. When parsing a value into a property of type java.lang.Class, the default class swap loaded the named class with initialization enabled, so input naming a class on the application classpath ran that class's static initializer.