CVE-2019-17638

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).