⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Not verified

How to Fix CVE-2026-23906: Authentication Bypass in Apache Druid

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityNot verified - see advisory
Actively exploited?Not currently listed in CISA KEV
Affected0.17.0 < 36.0.0
Fixed inSee vendor advisory
Type (CWE)CWE-287: Improper Authentication

What is CVE-2026-23906?

CVE-2026-23906 is an authentication bypass in Apache Druid. A flaw in the authentication or session-handling logic lets a remote attacker reach administrative functions without valid credentials. In several reported cases this leads directly to remote code execution. Vendor description: Affected Products and Versions * Apache Druid * Affected Versions: 0.17.0 through 35.x (all versions prior to 36.0.0) * Prerequisites: * druid-basic-security extension enabled * LDAP authenticator configured * Underlying LDAP server permits anonymous bind Vulnerability Description An authentication bypass vulnerability exists in Apache Druid when using the druid-basic-security extension with LDAP authentication. If the underlying LDAP server is configured to allow anonymous binds, an attacker can bypass authentication by providing an existing username with an empty password.

Why this CVE matters

Authentication bypass on a network appliance or admin console is a top-tier target. Once the attacker is past the login, every administrative endpoint becomes available, including the ones that change settings, upload firmware, or run shell commands.

For deployments of Apache Druid that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Even where exploitation has not been publicly observed, scanning for the vulnerable fingerprint is cheap and routine. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

Run the project-specific version command (for example httpd -v, tomcat version, or check pom.xml / package metadata) and compare against the advisory.

How to fix CVE-2026-23906

  1. Read the vendor advisory in full: https://lists.apache.org/thread/2x9rv3kv6t1p577lvq4z0rl0zlt9g4sr
  2. Upgrade Apache Druid to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Rotate any credentials, API keys, or session tokens that the vulnerable service touched. An unauthenticated RCE-class flaw means anything the process could see should be treated as exposed.
  5. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  6. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

Patch via the OS package manager


# Target fixed version: see advisory (https://lists.apache.org/thread/2x9rv3kv6t1p577lvq4z0rl0zlt9g4sr)
# Source advisory: https://lists.apache.org/thread/2x9rv3kv6t1p577lvq4z0rl0zlt9g4sr

# Debian / Ubuntu.
sudo apt update
sudo apt install --only-upgrade apache2
dpkg -s apache2 | grep -i version

# RHEL / Rocky / AlmaLinux / Fedora.
sudo dnf upgrade --refresh apache2 -y
rpm -q apache2

# openSUSE.
sudo zypper refresh
sudo zypper update apache2

# Restart any service backed by this package, then confirm the running version.
sudo systemctl restart apache2 2>/dev/null || true


# Vendor advisory: https://lists.apache.org/thread/2x9rv3kv6t1p577lvq4z0rl0zlt9g4sr
# Container image refresh.
docker pull <your-registry>/apache2:<patched-tag>
docker stop <your-app> && docker rm <your-app>
docker run -d --name <your-app> <your-registry>/apache2:<patched-tag>


# Windows side of the fleet - install equivalent vendor update.
Install-Module PSWindowsUpdate -Force -SkipPublisherCheck -Confirm:$false
Import-Module PSWindowsUpdate
Get-WindowsUpdate -AcceptAll -Install -AutoReboot

Verify the fix landed


# 1. Confirm the running version matches the fixed-in version listed above.
# 2. Re-scan with your vulnerability scanner (Nessus, Qualys, Tenable, OpenVAS).
#    The scanner should no longer flag this CVE on the patched target.
# 3. Inspect recent service / kernel logs for crash-loops or rollback events.
journalctl --since "10 minutes ago" | tail -50
dmesg --since "10 minutes ago" 2>/dev/null | tail -50

If you cannot patch immediately

Restrict access to the management interface to trusted internal IP addresses only. Block public access at the firewall and require VPN for any remote administration. Apply the patch as soon as a maintenance window allows.

How to verify the fix worked

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for unexpected administrator accounts in Apache Druid, scheduled tasks or cron jobs you did not create, new files in web-accessible directories, and outbound connections to addresses not in your baseline. Suspicious requests to the vulnerable endpoint immediately followed by successful 200-class responses with unusually large bodies are a strong indicator of exploitation.

Frequently asked questions

Is CVE-2026-23906 being exploited in the wild?

Public exploitation has not been confirmed by CISA at the time of writing. Treat the patch as time-sensitive anyway; reports often lag actual abuse.

Will a WAF or IDS rule fully mitigate CVE-2026-23906?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

Do I need to assume compromise if my Apache Druid was internet-facing and unpatched?

For an unauthenticated RCE-class flaw exposed to the public internet during the known exploitation window, yes. Review logs, rotate credentials the process could access, and look for unexpected accounts, scheduled tasks, or outbound connections.

References

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*