CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
AI Score
Confidence
High
gRPC contains a vulnerability that allows hpack table accounting
errors could lead to unwanted disconnects between clients and
servers in exceptional cases/Β Three vectors were found that allow
the following DOS attacks:
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 0βs can be added at the start of an integer. gRPCβs hpack
parser needed to read all of them before concluding a parse.
gRPCβs 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 etcβ¦