CVE-2025-40896: 
Homebrew vulnerability analysis and mitigation

CVE-2025-40896 is an improper certificate validation vulnerability in Nozomi Networks Arc that allows unauthenticated network attackers to perform man-in-the-middle (MitM) attacks against communications between Arc agents and Guardian or CMC systems. The vulnerability affects all Arc versions prior to 2.2.0 and was published on March 4, 2026. It carries a CVSS v3.1 base score of 4.8 (Medium) and a CVSS v4.0 base score of 6.3 (Medium) (Nozomi Advisory).

The root cause is CWE-295 (Improper Certificate Validation): when an Arc agent establishes a connection to a Guardian or CMC server, it fails to verify the server's TLS certificate, leaving the channel open to interception. An attacker positioned on the network path between the Arc agent and the Guardian/CMC can present a fraudulent certificate and intercept or manipulate the encrypted channel. Exploitation requires the attacker to have a network-adjacent position capable of intercepting traffic (attack requirements: PRESENT in CVSS v4.0), but no privileges or user interaction are needed. No public proof-of-concept exploit code has been identified (Nozomi Advisory).

A successful MitM attack can result in theft of the Arc client authentication token and sensitive operational data such as asset inventories and security alerts, impersonation of the Guardian or CMC server to the Arc agent, and injection of spoofed data — including false asset information or fabricated vulnerability reports — into the Guardian or CMC platform. Because Nozomi Networks products are widely deployed in OT/ICS environments, data integrity compromise could have downstream consequences for industrial security monitoring and incident response decisions (Nozomi Advisory).

There is no evidence of active in-the-wild exploitation or a publicly available proof-of-concept at this time. The EPSS score is approximately 0.02%, reflecting a low near-term exploitation probability. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. Exploitation requires a network-adjacent MitM position, which raises the practical bar for opportunistic attackers (Nozomi Advisory).

1. Reconnaissance: Identify network segments where Nozomi Networks Arc agents communicate with Guardian or CMC systems, targeting environments running Arc versions prior to 2.2.0.
2. Network Positioning: Gain a man-in-the-middle position on the network path between an Arc agent and its Guardian/CMC endpoint (e.g., via ARP spoofing, rogue access point, or compromised network device).
3. TLS Interception: Present a self-signed or attacker-controlled TLS certificate to the Arc agent during the TLS handshake. Because the Arc agent does not validate the server certificate, it accepts the fraudulent certificate and establishes an encrypted session with the attacker.
4. Traffic Interception: Decrypt and inspect the Arc agent's communications, extracting the client authentication token and sensitive data such as asset lists and security alerts.
5. Data Manipulation or Impersonation: Optionally relay modified data to the legitimate Guardian/CMC (injecting false asset information or fabricated vulnerability data) or use the stolen client token to impersonate the Arc agent in subsequent sessions (Nozomi Advisory).

• Network: Unexpected TLS certificates presented on Guardian/CMC communication ports that do not match the expected issuer or fingerprint; ARP table anomalies or duplicate MAC entries on segments hosting Arc agents.
• Logs: Arc agent connection logs showing TLS handshake completions with certificates from unexpected issuers or with mismatched hostnames; repeated reconnection attempts or session resets between Arc agents and Guardian/CMC.
• Behavioral: Unexpected or duplicate asset entries appearing in Guardian/CMC dashboards; alerts or vulnerability data inconsistent with known network state, potentially indicating injected spoofed data.

Nozomi Networks has released Arc version 2.2.0, which addresses this vulnerability by enforcing proper TLS server certificate validation. Organizations should upgrade all Arc agents to version 2.2.0 or later as the primary remediation. As interim mitigations, implement network segmentation to restrict and monitor communication channels between Arc agents and Guardian/CMC systems, deploy intrusion detection/prevention systems to flag anomalous MitM activity, and consider enforcing mutual TLS authentication and certificate pinning for agent-to-server communications (Nozomi Advisory).

Coverage of CVE-2025-40896 has been limited to automated vulnerability tracking platforms and aggregators such as Vulners, VulDB, and ENISA's EUVD. A brief technical summary was published by Infinit Security (Infinit Security). No significant vendor statements beyond the official advisory, notable independent researcher commentary, or broad media coverage have been identified at this time.