[JENKINS-72732] ActiveDirectory authentication error with german umlaut in user DN

Hi.

I am using Ldap plugin to authenticate to ActiveDirectory, and all users not having german umlaut like "ÄÖÜ" in their user-dn can login fine:

For example:

DN: CN=Franz Tester,OU=Users,DC=example,DC=com

sAMAccountName: tester201

( please see Picture1 too)

All users, with ÜÖÄ in its surname or lastname get an authentication error.

DN:: base64 encoded string

sAMAccountName: tester202

( please see Picture2 too)

I know, it is recommended not to use german umlaut in the DN, but my company has configured it like this, and i cannot change it.

I am not a developer, so i cannot help to fix this problem, but i hope someone is here to help me.

I have tested several configurations with different ldap queries and changed my password to something simple, but nothing works. So i have no further idea and think, it could be a problem with the plugin code to not decode the DN correctly, maybe.

Thank's in advance for your help!

---
Originally reported by jcb, imported from: ActiveDirectory authentication error with german umlaut in user DN

• status: Open
  
• priority: Critical
  
• component(s): ldap-plugin
  
• resolution: Unresolved
  
• votes: 0
  
• watchers: 1
  
• imported: 2025-12-09
  

Raw content of original issue

Hi.


I am using Ldap plugin to authenticate to ActiveDirectory, and all users not having german umlaut like "ÄÖÜ" in their user-dn can login fine:


For example:

DN: CN=Franz Tester,OU=Users,DC=example,DC=com


sAMAccountName: tester201


( please see Picture1 too)


All users, with ÜÖÄ in its surname or lastname get an authentication error.


DN:: base64 encoded string


sAMAccountName: tester202


( please see Picture2 too)


I know, it is recommended not to use german umlaut in the DN, but my company has configured it like this, and i cannot change it.

I am not a developer, so i cannot help to fix this problem, but i hope someone is here to help me.

I have tested several configurations with different ldap queries and changed my password to something simple, but nothing works. So i have no further idea and think, it could be a problem with the plugin code to not decode the DN correctly, maybe.


Thank's in advance for your help!

environment

```
Openjdk-21

RHEL 9.3

Jenkins 2.426.3

LDAP plugin: latest
```

3 attachments

- [Java_log.txt](https://issues.jenkins.io/secure/attachment/62114/Java_log.txt)
- [Picture1.png](https://issues.jenkins.io/secure/attachment/62113/Picture1.png)
> 
- [Picture2.png](https://issues.jenkins.io/secure/attachment/62112/Picture2.png)
> 

Start by reviewing the attached Java_log.txt and the ldap-plugin authentication flow, comparing the successful ASCII DN with the failing DN containing German umlauts. Reproduce the failure against ActiveDirectory using the provided environment details. Done means users with umlauts in their user DN can authenticate successfully, with regression coverage if the project has an appropriate test location.

Written by the indexing model from the issue text.