CVE-2023-33953
Assigner: Google
Published: 2023-08-09T12:54:47.415Z
State: PUBLISHED
affected: defaultStatus: unaffected
product: gRPC
vendor: Google
versions: lessThan: 1.56.1
status: affected
version: 0
versionType: custom
descriptions: supportingMedia: base64: no
type: text/html
value: gRPC contains a vulnerability that allows hpack table accounting errors could lead to unwanted disconnects between clients and servers in exceptional cases/&nbsp;Three vectors were found that allow the following DOS attacks:<br><br>- Unbounded memory buffering in the HPACK parser<br>- Unbounded CPU consumption in the HPACK parser<br><br>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.<br><br>The unbounded memory buffering bugs:<br><br>- 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.<br>- 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.<br>- 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…
value: 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…
impacts: capecId: CAPEC-220
descriptions: value: CAPEC-220 Client-Server Protocol Manipulation
metrics: cvssV3_1: attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 7.5
baseSeverity: HIGH
confidentialityImpact: NONE
integrityImpact: NONE
privilegesRequired: NONE
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
version: 3.1
format: CVSS
scenarios: value: GENERAL
problemTypes: descriptions: cweId: CWE-834
description: CWE-834 Excessive Iteration
type: CWE
descriptions: cweId: CWE-789
description: CWE-789 Memory Allocation with Excessive Size Value
type: CWE
source: discovery: UNKNOWN
title: Denial-of-Service in gRPC
x_generator: engine: Vulnogram 0.1.0-dev