CVE-2025-40896: Nozomi Networks Arc MitM Vulnerability

CVE-2025-40896 Overview

CVE-2025-40896 is a certificate validation bypass vulnerability affecting Nozomi Networks Arc agents. The vulnerability stems from improper verification of server certificates when an Arc agent establishes connections to Guardian or Central Management Console (CMC) systems. This security flaw (CWE-295: Improper Certificate Validation) enables attackers positioned on the network to intercept and manipulate communications between Arc agents and management infrastructure.

Critical Impact

Successful exploitation enables man-in-the-middle attacks that could result in theft of client tokens and sensitive operational technology (OT) data, server impersonation, or injection of spoofed asset information and false vulnerability data into Guardian or CMC systems.

Affected Products

• Nozomi Networks Arc (all versions prior to patched release)
• Guardian systems when connected via vulnerable Arc agents
• Central Management Console (CMC) when connected via vulnerable Arc agents

Discovery Timeline

• 2026-03-04 - CVE CVE-2025-40896 published to NVD
• 2026-03-05 - Last updated in NVD database

Technical Details for CVE-2025-40896

Vulnerability Analysis

This vulnerability exists in the TLS/SSL certificate verification logic within the Nozomi Networks Arc agent software. When Arc agents initiate secure connections to Guardian or CMC servers, the implementation fails to properly validate the authenticity of server certificates. This fundamental cryptographic security control bypass means the Arc agent cannot distinguish between legitimate management servers and attacker-controlled systems presenting fraudulent certificates.

The impact is particularly concerning in operational technology (OT) and industrial control system (ICS) environments where Nozomi Networks products are commonly deployed. Attackers exploiting this vulnerability could intercept sensitive asset discovery data, security alerts, and vulnerability information flowing between distributed Arc agents and centralized management platforms.

Root Cause

The root cause is classified as CWE-295 (Improper Certificate Validation). The Arc agent's TLS implementation does not enforce proper certificate chain validation, certificate revocation checking, or hostname verification when establishing connections to Guardian or CMC endpoints. This allows self-signed, expired, or fraudulently issued certificates to be accepted without raising security errors.

Attack Vector

The attack requires network positioning that allows the adversary to intercept traffic between Arc agents and their management servers. This network-based attack vector does not require authentication or user interaction. An attacker would:

1. Position themselves on the network path between an Arc agent and Guardian/CMC server
2. Intercept the TLS handshake and present a malicious certificate
3. Establish separate encrypted sessions with both the agent and the legitimate server
4. Relay, modify, or inject traffic while maintaining the appearance of normal operations

The vulnerability enables several attack outcomes including theft of authentication tokens, exfiltration of asset inventories and security alerts, impersonation of management servers to issue malicious commands, and injection of false vulnerability or asset data to manipulate security monitoring.

Detection Methods for CVE-2025-40896

Indicators of Compromise

• Unexpected certificate fingerprints observed during Arc agent connections to Guardian/CMC
• Network traffic anomalies showing Arc agents connecting to IP addresses not associated with legitimate Guardian/CMC servers
• Certificate warnings or errors in system logs that were previously ignored or suppressed
• Inconsistent or suspicious asset data appearing in Guardian/CMC that doesn't match known network inventory

Detection Strategies

• Deploy network monitoring to identify TLS sessions with certificate anomalies between Arc agents and management infrastructure
• Implement certificate pinning detection to identify when Arc agents connect using unexpected certificates
• Monitor for DNS spoofing or ARP poisoning attacks that could facilitate man-in-the-middle positioning
• Review Arc agent logs for connection establishment patterns to unauthorized endpoints

Monitoring Recommendations

• Enable verbose logging on Arc agents and Guardian/CMC systems to capture connection establishment details
• Implement network traffic analysis between OT monitoring segments and management infrastructure
• Deploy intrusion detection signatures to identify TLS interception attempts
• Establish baseline communication patterns for Arc agents to detect deviations

How to Mitigate CVE-2025-40896

Immediate Actions Required

• Review the Nozomi Networks Security Advisory for patched version information
• Audit network architecture to identify exposure of Arc agent to Guardian/CMC communication paths
• Implement network segmentation to limit attacker positioning opportunities
• Monitor for signs of active exploitation while preparing for patch deployment

Patch Information

Nozomi Networks has released a security advisory addressing this vulnerability. Organizations should consult the official Nozomi Networks Security Advisory NN-2025:18-01 for specific patch versions and upgrade instructions. Apply the latest Arc agent version that includes proper certificate validation to remediate this vulnerability.

Workarounds

• Implement strict network segmentation between Arc agents and Guardian/CMC systems to reduce man-in-the-middle attack surface
• Deploy network-level encryption such as IPsec VPN tunnels for Arc agent communications as an additional protection layer
• Enable network monitoring and alerting for traffic anomalies on paths between Arc agents and management systems
• Consider implementing 802.1X port-based authentication to prevent unauthorized devices from positioning on critical network segments

# Network segmentation verification example
# Verify that Arc agent to Guardian/CMC traffic traverses only trusted network paths
# Review firewall rules and VLAN configurations

# Example: Check for unexpected hosts in the network path
traceroute guardian.internal.network

# Monitor for ARP anomalies that could indicate MITM positioning
arp -a | grep guardian