HTTP Proxy authentication is broken - error "MD5 This constraint may be relaxed by setting the "http.auth.digest.reEnabledAlgorithms" system property."

Problem

Check connection under File | Settings | Appearance & Behavior | System Settings | HTTP Proxy leads to a popup Check Proxy Settings, Problem with connection: Request failed with status code 407.

There is the following log in idea.log(to find the logs, check Locating IDE log files article): 2024-08-07 10:50:31,004 [  50811]   INFO - sun.net.www.protocol.http.HttpURLConnection - Rejecting digest authentication with insecure algorithm: MD5 This constraint may be relaxed by setting the "http.auth.digest.reEnabledAlgorithms" system property.

Cause

It's caused by the JBR upgrade, MD5 digest authentication was disabled by default in JDK19: https://bugs.openjdk.org/browse/JDK-8282649

Resolution

• Navigate to Help | Edit Custom VM Options
• Add the following line: -Dhttp.auth.digest.reEnabledAlgorithms=MD5
• Restart IDE