When using SCM over http (tested in my case with Git), Maven SCM should encode username and password before using them with URL.
In order to reproduce, try to create a release with Maven Release and a user with a password containing @ character, it will fail.
Please find bellow cmd output :
[INFO] Executing: /bin/sh -c cd /DATA/jenkins/workspace/path && git push http://username:*********@git.forge/git/project/ master:master
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-release-plugin:2.4:prepare (default-cli) on project project: Unable to commit files
The git-push command failed.
error: Couldn't resolve host '@*******@git.forge' while accessing http://username:*********@git.forge/git/project/info/refs
fatal: HTTP request failed