1. Introduction
Zebedee Server Detection indicates a tunneling service is running on a remote host. This allows TCP and UDP connections to be securely forwarded, potentially bypassing firewall rules and exposing internal services. Systems affected are typically Linux servers where the Zebedee software has been installed. A successful exploit could compromise confidentiality, integrity, and availability of connected systems.
2. Technical Explanation
The remote host is running Zebedee in server mode, creating a tunnel endpoint. An attacker can connect to this endpoint and redirect traffic through it to other hosts on the network. This requires the target system to be accessible from the internet or an internal network where the attacker has access. There isn’t a specific CVE associated with simply *running* Zebedee in server mode; the risk depends entirely on how it is configured and used.
- Root cause: The software is running in server mode, listening for incoming connections.
- Exploit mechanism: An attacker connects to the Zebedee server and configures a tunnel to an internal host. This forwards traffic through the server. For example, an attacker could use Zebedee to access a database server normally protected by a firewall.
- Scope: Linux servers with Zebedee installed.
3. Detection and Assessment
Confirming whether a system is vulnerable involves checking for the running Zebedee service. A quick check can identify if it’s listening on a port, while more thorough methods involve examining the configuration.
- Quick checks: Use `netstat -tulnp` or `ss -tulnp` to see if any processes are listening on ports used by Zebedee (default is 9999).
- Scanning: Nessus plugin ID 16874 may detect this. This is an example only, and results should be verified manually.
- Logs and evidence: Check system logs for Zebedee startup messages or connection attempts.
netstat -tulnp | grep zebedee
4. Solution / Remediation Steps
Fixing this issue involves ensuring the use of Zebedee aligns with your security policy. If it’s not required, stop and disable the service. If required, review its configuration carefully.
4.1 Preparation
- Dependencies: Ensure no other services rely on Zebedee’s tunneling functionality. A roll back plan is to restore the backed-up config and restart the service.
- Change window needs: Changes may require a short maintenance window, depending on service dependencies. Approval from the system owner may be needed.
4.2 Implementation
- Step 1: If Zebedee is not required, disable the service: `systemctl disable zebedee`.
- Step 2: Remove the Zebedee package if no longer needed: `apt remove zebedee` or equivalent for your distribution.
- Step 3: If Zebedee *is* required, review its configuration file (usually `/etc/zebedee/zebedee.conf`) to ensure only authorized tunnels are allowed.
4.3 Config or Code Example
Before
# /etc/zebedee/zebedee.conf
allow_all = true
After
# /etc/zebedee/zebedee.conf
allow_all = false
allowed_hosts = 192.168.1.0/24,10.0.0.5
4.4 Security Practices Relevant to This Vulnerability
List only practices that directly address this vulnerability type. Use neutral wording and examples instead of fixed advice. For example: least privilege, input validation, safe defaults, secure headers, patch cadence.
- Practice 1: Least privilege – restrict access to the Zebedee service to authorized users only.
- Practice 2: Network segmentation – limit network access to the server hosting Zebedee.
4.5 Automation (Optional)
#!/bin/bash
# Check if zebedee is running and disable it if allow_all is true
if systemctl is-active --quiet zebedee; then
if grep -q "allow_all = true" /etc/zebedee/zebedee.conf; then
systemctl stop zebedee
systemctl disable zebedee
echo "Zebedee disabled due to allow_all being true."
fi
fi
5. Verification / Validation
Confirm the fix worked by checking that the service is stopped or configured correctly. A negative test involves attempting an unauthorized connection.
- Post-fix check: `systemctl status zebedee` should show the service as inactive if disabled, or `netstat -tulnp | grep zebedee` should return no results.
- Re-test: Run the earlier detection (`netstat -tulnp | grep zebedee`) to confirm it no longer detects Zebedee listening on any ports.
- Smoke test: If Zebedee is required, verify authorized tunnels still function as expected.
- Monitoring: Monitor system logs for unexpected Zebedee activity or connection attempts.
systemctl status zebedee
6. Preventive Measures and Monitoring
Suggest only measures that are relevant to the vulnerability type. Use “for example” to keep advice conditional, not prescriptive.
- Baselines: Update your server hardening baseline to include a check for unnecessary tunneling services like Zebedee.
- Pipelines: Include static analysis checks in your CI/CD pipeline to identify potentially insecure configurations.
- Asset and patch process: Regularly review installed software on servers to ensure only authorized applications are present.
7. Risks, Side Effects, and Roll Back
- Risk or side effect 1: Disabling Zebedee may break applications that rely on its tunneling functionality.
- Risk or side effect 2: Incorrectly configuring allowed hosts can block legitimate traffic.
- Roll back: If disabled, re-enable the service with `systemctl enable zebedee` and `systemctl start zebedee`. Restore the original configuration file if necessary.
8. References and Resources
- Vendor advisory or bulletin: http://www.winton.org.uk/zebedee/