You've just enabled Global Security in Jenkins, only to find yourself completely locked out of the interface with the dreaded "anonymous is missing the Overall/Read permission" error. The stack trace shows the security subsystem preventing anonymous access - exactly what we wanted, but now we can't even log in to configure proper permissions.

Jenkins stores its security configuration in config.xml within the Jenkins home directory. When you enabled security, it modified this file to implement access controls. The key elements we need to examine are:

<useSecurity>true</useSecurity>
<authorizationStrategy class="hudson.security.FullControlOnceLoggedInAuthorizationStrategy">
  <denyAnonymousReadAccess>true</denyAnonymousReadAccess>
</authorizationStrategy>

Here's how to regain access when completely locked out:

1. Locate your Jenkins home directory (typically /var/lib/jenkins on Linux or C:\Program Files (x86)\Jenkins on Windows)
2. Make a backup of config.xml
3. Edit config.xml and find the security section
4. Change these values:

   <useSecurity>false</useSecurity>
   <authorizationStrategy class="hudson.security.AuthorizationStrategy$Unsecured"/>
   

5. Save the file and restart Jenkins service:

   sudo systemctl restart jenkins  # Linux
   net stop jenkins & net start jenkins  # Windows
   

Once you regain access, properly configure security:

// Recommended matrix-based security setup
<authorizationStrategy class="hudson.security.GlobalMatrixAuthorizationStrategy">
  <permission>hudson.model.Hudson.Read:anonymous</permission>
  <permission>hudson.model.Hudson.Administer:admin_user</permission>
</authorizationStrategy>

For automated environments, create init.groovy in $JENKINS_HOME/init.groovy.d/:

import jenkins.model.*
import hudson.security.*

def instance = Jenkins.getInstance()

def strategy = new GlobalMatrixAuthorizationStrategy()
strategy.add(Jenkins.READ,'anonymous')
strategy.add(Jenkins.ADMINISTER,'admin')
instance.setAuthorizationStrategy(strategy)

instance.setSecurityRealm(new HudsonPrivateSecurityRealm(false))
instance.save()

• Always create an admin account before enabling security
• Test security changes in a staging environment first
• Keep the config.xml backup
• Consider setting up emergency SSH access

When you enable global security in Jenkins and immediately encounter the "anonymous is missing the Overall/Read permission" error, you're essentially locked out of your Jenkins instance. This occurs because Jenkins has strict security measures that prevent anonymous access by default when security is enabled, and you haven't configured any authorized users yet.

The stack trace clearly shows the security chain reaction:

hudson.security.AccessDeniedException2: anonymous is missing the Overall/Read permission
at hudson.security.ACL.checkPermission(ACL.java:54)

Jenkins security model requires explicit permissions for all operations. Without proper configuration, the system falls back to anonymous access which now fails due to tightened security.

The fastest way to regain access is to revert the security settings by editing Jenkins' config file:

1. Navigate to your Jenkins home directory (typically /var/lib/jenkins on Linux or C:\Program Files (x86)\Jenkins on Windows)
2. Open config.xml in a text editor
3. Find the <useSecurity>true</useSecurity> line
4. Change it to <useSecurity>false</useSecurity>
5. Save the file and restart Jenkins service (sudo service jenkins restart or through services manager)

Once you regain access, you should properly configure security:

// Sample Groovy init script for automated security setup
import jenkins.model.*
import hudson.security.*

def instance = Jenkins.getInstance()

// Create the user/group you want as admin
def hudsonRealm = new HudsonPrivateSecurityRealm(false)
hudsonRealm.createAccount("admin","password123")
instance.setSecurityRealm(hudsonRealm)

// Authorization strategy
def strategy = new GlobalMatrixAuthorizationStrategy()
strategy.add(Jenkins.ADMINISTER, "admin")
instance.setAuthorizationStrategy(strategy)

// Enable security
instance.setSecurityRealm(hudsonRealm)
instance.save()

If you can't access the file system directly, try using Jenkins CLI:

java -jar jenkins-cli.jar -s http://localhost:8080 groovy =
// Paste the above Groovy script here
// Press Ctrl+D (Linux/Mac) or Ctrl+Z (Windows) to execute

Always test security changes in a staging environment first. Consider these best practices:

• Have at least one admin account configured before enabling security
• Keep backup copies of config.xml
• Document your security settings
• Consider using Jenkins Configuration as Code plugin for reproducible security setups

If the basic fix doesn't work, check these additional areas:

# Verify file permissions
ls -la /var/lib/jenkins/config.xml

# Check Jenkins logs
tail -f /var/log/jenkins/jenkins.log