- update to 1.55.1:
* Fix memory leak
This commit fixes memory leak that happens when
PUSH_PROMISE or HEADERS frame cannot be sent, and
nghttp2_on_stream_close_callback fails with a fatal error.
For example, if GOAWAY frame has been received, a
HEADERS frame that opens new stream cannot be sent.
This issue has already been made public via CVE-2023-35945
by envoyproxy/envoy project. During embargo period, the
patch to fix this bug was accidentally submitted to
nghttp2/nghttp2 repository [2]. And they decided to
disclose CVE early. I was notified just 1.5 hours
before disclosure. I had no time to respond.
PoC described in [1] is quite simple, but I think it is
not enough to trigger this bug. While it is true that
receiving GOAWAY prevents a client from opening new stream,
and nghttp2 enters error handling branch, in order to cause
the memory leak, nghttp2_session_close_stream function
must return a fatal error.
NGHTTP2_ERR_NOMEM, as its name suggests, indicates out of
memory. It is unlikely that a process gets short of
memory with this simple PoC scenario unless application
does something memory heavy processing.
* NGHTTP2_ERR_CALLBACK_FAILURE is returned from application
defined callback function (nghttp2_on_stream_close_callback, in
this case), which indicates something fatal happened inside a
callback, and a connection must be closed immediately without
any further action. As nghttp2_on_stream_close_error_callback
documentation says, any error code other than 0 or
NGHTTP2_ERR_CALLBACK_FAILURE is treated as fatal