CVE-2023-33953

gRPC contains a vulnerability that allows hpack table accounting errors
could lead to unwanted disconnects between clients and servers in
exceptional cases/ Three vectors were found that allow the following DOS
attacks: - Unbounded memory buffering in the HPACK parser - Unbounded CPU
consumption in the HPACK parser The unbounded CPU consumption is down to a
copy that occurred per-input-block in the parser, and because that could be
unbounded due to the memory copy bug we end up with an O(n^2) parsing loop,
with n selected by the client. The unbounded memory buffering bugs: - The
header size limit check was behind the string reading code, so we needed to
first buffer up to a 4 gigabyte string before rejecting it as longer than 8
or 16kb. - HPACK varints have an encoding quirk whereby an infinite number
of 0’s can be added at the start of an integer. gRPC’s hpack parser needed
to read all of them before concluding a parse. - gRPC’s metadata overflow
check was performed per frame, so that the following sequence of frames
could cause infinite buffering: HEADERS: containing a: 1 CONTINUATION:
containing a: 2 CONTINUATION: containing a: 3 etc…