In Eclipse Jetty, versions 9.4.27.v20200227 to 9.4.29.v20200521, in case of too large response headers, Jetty throws an exception to produce an HTTP 431 error. When this happens, the ByteBuffer containing the HTTP response headers is released back to the ByteBufferPool twice. Because of this double release, two threads can acquire the same ByteBuffer from the pool and while thread1 is about to use the ByteBuffer to write response1 data, thread2 fills the ByteBuffer with other data. Thread1 then proceeds to write the buffer that now contains different data. This results in client1, which issued request1 seeing data from another request or response which could contain sensitive data belonging to client2 (HTTP session ids, authentication credentials, etc.). If the Jetty version cannot be upgraded, the vulnerability can be significantly reduced by configuring a responseHeaderSize significantly larger than the requestHeaderSize (12KB responseHeaderSize and 8KB requestHeaderSize).

In Eclipse Jetty versions 9.4.21.v20190926, 9.4.22.v20191022, and 9.4.23.v20191118, the generation of default unhandled Error response content (in text/html and text/json Content-Type) does not escape Exception messages in stacktraces included in error output.

In Eclipse Jetty version 9.2.26 and older, 9.3.25 and older, and 9.4.15 and older, the server is vulnerable to XSS conditions if a remote client USES a specially formatted URL against the DefaultServlet or ResourceHandler that is configured for showing a Listing of directory contents.

In Eclipse Jetty version 7.x, 8.x, 9.2.27 and older, 9.3.26 and older, and 9.4.16 and older, the server running on any OS and Jetty version combination will reveal the configured fully qualified directory base resource location on the output of the 404 error for not finding a Context that matches the requested path. The default server behavior on jetty-distribution and jetty-home will include at the end of the Handler tree a DefaultHandler, which is responsible for reporting this 404 error, it presents the various configured contexts as HTML for users to click through to. This produced HTML includes output that contains the configured fully qualified directory base resource location for each context.

In Eclipse Jetty version 9.3.x and 9.4.x, the server is vulnerable to Denial of Service conditions if a remote client sends either large SETTINGs frames container containing many settings, or many small SETTINGs frames. The vulnerability is due to the additional CPU and memory allocations required to handle changed settings.