Core Vulnerability Details

CVE-ID: CVE-2026-25769
Severity: Critical
CVSS Score: 9.1
CWE: CWE-502 : Deserialization of Untrusted Data
Affected Versions: Wazuh 4.0.0 → 4.14.2
Patched Version: 4.14.3

Vulnerability Class:
Remote Code Execution via insecure Python deserialization.

Attack Surface:
Wazuh cluster communication between worker and master nodes.

Root Cause Components:

1. Trust boundary failure
   • Master node trusts authenticated worker messages.
   • No validation of message content.
2. Unsafe deserialization
   • json.loads() uses a custom object_hook.
   • Hook dynamically imports Python modules.
   • No module allowlist restriction.

Affected Code Location

File Path:

framework/wazuh/core/cluster/common.py

Function:

as_wazuh_object()

Relevant Lines:

1830–1866

Critical Mechanism:

The function is registered as:

json.loads(..., object_hook=as_wazuh_object)

Security Impact:

Every deserialized JSON object executes logic inside:

as_wazuh_object()

This allows:

Arbitrary Python module import

Arbitrary function execution

Result:

Remote Code Execution (RCE)
on master node

Attack Path Overview

Initial Requirement

Attacker must control:

A compromised worker node

This is a post-compromise lateral escalation vector.

Exploitation Flow

1. Compromise worker node.
2. Craft malicious JSON payload.
3. Send payload through cluster communication.
4. Master deserializes payload.
5. Python module import executes attacker-controlled logic.
6. System command runs on master.

Privilege Outcome

Typical result:

Root-level RCE
on master node

Impact expands cluster-wide compromise risk.

Cluster Communication Details

Protocol Characteristics

Communication occurs via:

TCP port: 1516
Encryption: Fernet

Important Analyst Insight:

Encryption hides payload content from network inspection.

Malicious payload:

Structurally identical
to legitimate DAPI traffic

Detection complexity:

High

Exploit Payload Characteristics

Payload Behavior

Malicious payload:

Valid JSON structure
Contains object fields
Triggers module import
Executes function
Runs system command

Exploit Class

Deserialization-based RCE
via object hook abuse

Detection Notes

Detection requires multi-layer visibility.

Network-Level Indicators

Port Monitoring

Watch:

TCP 1516

Indicators:

• Unexpected worker communication spikes
• Unknown worker IP connections
• Lateral movement patterns

Host-Level Indicators

Primary detection surface:

Master node process tree

Look for:

Unexpected child processes
spawned by Wazuh components

Typical suspicious patterns:

wazuh -> python -> shell -> command

Examples of suspicious child process activity:

• Shell execution
• System command invocation
• Interpreter spawning

SIEM Detection Opportunities

Focus queries on:

Anomalous child processes
spawned by wazuh services

High-value telemetry sources:

• Process creation logs
• Auditd logs
• Sysmon logs
• EDR telemetry

Mitigation Strategy

Primary Remediation

Upgrade immediately:

Wazuh ≥ 4.14.3

Security change introduced:

Module allowlist
inside as_wazuh_object()

Prevents:

Arbitrary module import

Interim Mitigations (If Upgrade Not Possible)

Network Controls

Restrict cluster communication:

Port: 1516

Allow only:

Known worker IP addresses

Apply:

Firewall rules
ACL restrictions
Network isolation

Worker Node Security

Monitor worker integrity:

Focus areas:

• Unauthorized modifications
• Suspicious processes
• Persistence mechanisms

Reason:

Worker compromise enables master compromise

Network Segmentation

Implement:

Worker ↔ Master segmentation

Objective:

Reduce lateral movement risk

Cluster Key Hygiene

Rotate:

Cluster keys

Required:

After suspected compromise
Regular security schedule

Purpose:

Invalidate attacker access

Long-Term Hardening

Principle of Least Privilege

Apply to:

Wazuh service account

Restrict:

• File access
• Command execution
• Privileged operations

Logging Strategy

Enable:

Audit logging
for cluster communication

Capture:

• Message activity
• Process spawning
• Cluster events

File Integrity Monitoring

Deploy on:

Master node

Monitor:

• System binaries
• Configuration files
• Cluster modules

Detect:

Unauthorized file changes

LocalClient Security Review

Restrict:

User access
Process interaction

Control:

LocalClient execution permissions

Threat Modeling Insights

Trust Boundary Failure

Critical architectural flaw:

Authenticated ≠ Trusted

Even trusted nodes must validate:

Content
Behavior
Intent

Risk Amplification Factor

Cluster architecture risk:

Worker compromise → Master compromise
→ Full cluster takeover

This vulnerability enables:

Privilege escalation

Lateral movement

Persistence

Defensive Takeaways

Key Lessons

1. Never deserialize untrusted data without validation.
2. Avoid dynamic module imports during parsing.
3. Enforce allowlists for executable logic.
4. Monitor trusted internal communication paths.
5. Assume internal compromise is possible.

High-Value Analyst Memory Points

• CVE-2026-25769 is a cluster trust abuse vulnerability.
• Exploitation requires worker compromise.
• Payload travels over encrypted TCP 1516.
• Detection depends primarily on host telemetry, not network inspection.
• Patch introduces module allowlisting, eliminating arbitrary imports.
• Failure to patch allows root-level RCE on master node.

THM Wazuh: CVE-2026-25769 Room Answers

What is the name of the Python file containing the vulnerable as_wazuh_object() function?

common.py

What Python function is used to dynamically load modules from the __module__ field without validation?

import_module

What encryption scheme is used to protect cluster communication between worker and master?

Fernet

On which TCP port does the master node listen for cluster communication?

1516

What Python module does the exploit payload specify in the __module__ field to achieve command execution?

subprocess

What is the request_type value used in the exploit payload to target the master node?

local_master

What are the contents of root.txt on the master server?

THM{WAZUH_RCE_COMPLETED}