Encountering the "Too Many Inbound Bytes Received" error in Neo4j, particularly when using Single Sign-On (SSO) for connection, can be caused by the authentication token exceeding the 8KB limit. This is often a result of the user being part of a large number of Identity Provider IdP groups. 

The connection using SSO will fail with the following errors:

In Browser ( using :debug):

client side SSO flow completed but Neo4j Browser failed to connect to neo4j. 
Server side logs (security.log or debug.log) may contain more information."
 

Error in Neo4j debug.log:

2023-09-22 14:28:48.615+0000 ERROR [o.n.b.t.p.HouseKeeper] Fatal error occurred 
when handling a client connection: 
[id: 0xcb06f268, L:/0:0:0:0:0:0:0:1:7617 ! R:/0:0:0:0:0:0:0:1:61416]
org.neo4j.bolt.runtime.BoltConnectionFatality: A connection '[id: 0xcb06f268, L:/0:0:0:0:0:0:0:1:7617 ! R:/0:0:0:0:0:0:0:1:61416]' 
is terminated because too many inbound bytes received before 
the client is authenticated.
Max bytes allowed: 8192. Bytes received: 8388.
at org.neo4j.bolt.transport.pipeline.BytesAccumulator.channelRead(BytesAccumulator.java:55) ~[neo4j-bolt-4.4.25.jar:4.4.25]

NeoDash SSO connection will also fail with this error:

Unable to establish connection:

Value of size 8388 exceeded limit of 8192

How to solve this problem?

Inspect the authentication token using your Browser developer tools. Detailed steps explained here. 

In your web Browser developer tools you can check the token (access_token or id_token) 

Open in JWT.io and copy the SSO token to check why the token exceeds the 8KB limit. In the example below, the user is part of a large number of IdP groups:

Work with the IdP administrator to reduce the size of the user token if possible. The 8KB limit was introduced to prevent potential DDoS attacks and cannot be left unlimited.

Alternatively, you can increase this limit, you have the option to utilise a specific internal parameter. Please add the following line to your neo4j.conf and restart the server: 
 

Neo4j V4

dbms.connector.bolt.unsupported_unauth_max_inbound_bytes=16384

This parameter was renamed in Neo4j V5 to: 

internal.server.bolt.unauth_max_inbound_bytes=16384