CVE-2026-40118: Arcserve UDP Console Info Disclosure Flaw

CVE-2026-40118 Overview

CVE-2026-40118 affects Arcserve UDP Console, a management interface for the Arcserve Unified Data Protection backup product. The flaw is classified as an incorrectly specified destination in a communication channel [CWE-941]. When an operator configures the activation server hostname to a dummy or attacker-controlled URL, the product transmits data to that unintended destination. This behavior results in information disclosure to a host the application should not contact. The issue was published to the National Vulnerability Database on April 16, 2026, and last modified on April 17, 2026.

Critical Impact

Misconfiguration of the activation server hostname causes Arcserve UDP Console to send sensitive communications to an attacker-controlled endpoint, leaking information over the network.

Affected Products

• Arcserve UDP Console (Unified Data Protection management console)
• Refer to the Arcserve Knowledge Base Article for specific affected versions
• See the JVN Security Vulnerability Report for vendor confirmation

Discovery Timeline

• 2026-04-16 - CVE-2026-40118 published to NVD
• 2026-04-17 - Last updated in NVD database

Technical Details for CVE-2026-40118

Vulnerability Analysis

The vulnerability resides in how Arcserve UDP Console handles the activation server hostname configuration. The application accepts a user-supplied hostname without sufficient validation against an allowlist of trusted activation endpoints. When the value is set to a dummy or unintended URL, the console initiates outbound communications to that destination. Data intended for the legitimate activation service is sent to whichever host the operator entered, exposing it to any party controlling that domain. The weakness maps to [CWE-941], Incorrectly Specified Destination in Communication Channel.

Root Cause

The root cause is the absence of strict destination validation in the activation workflow. The product trusts the configured hostname implicitly and does not verify whether the target represents a genuine Arcserve activation server. There is no certificate pinning or hostname allowlist enforcement that would prevent communication with arbitrary domains. As a result, configuration errors translate directly into information disclosure.

Attack Vector

Exploitation requires user interaction, specifically an administrator entering a dummy or malicious activation server hostname into the console configuration. An attacker who controls the resulting destination domain receives any data the console transmits during activation flows. The attack vector is network-based, but exploitation is passive on the attacker side and depends on the configuration mistake or social engineering that produces it. The EPSS score is 0.036% with a percentile of 10.8, indicating low observed exploitation likelihood.

No verified proof-of-concept code is available. See the JVN Security Vulnerability Report and the Arcserve Knowledge Base Article for technical details.

Detection Methods for CVE-2026-40118

Indicators of Compromise

• Outbound DNS resolution or HTTPS connections from UDP Console hosts to domains that are not official Arcserve activation endpoints.
• Activation server configuration entries containing test, placeholder, or non-Arcserve hostnames.
• TLS handshakes from the console process targeting unexpected certificate subjects or unknown certificate authorities.

Detection Strategies

• Audit the UDP Console configuration files and registry entries for the activation server hostname value and compare against the vendor-approved URL.
• Enable egress monitoring on network segments hosting Arcserve UDP Console to flag connections outside the expected activation domain.
• Correlate process-level network telemetry on the management server to attribute outbound traffic to the console binary specifically.

Monitoring Recommendations

• Log all administrative changes to UDP Console activation settings and forward them to a central logging platform for review.
• Maintain a baseline of legitimate destination hosts contacted by the console and alert on deviations.
• Inspect proxy and firewall logs for HTTP or HTTPS requests originating from the console host that target non-Arcserve domains.

How to Mitigate CVE-2026-40118

Immediate Actions Required

• Verify the activation server hostname configured in Arcserve UDP Console matches the official value documented by Arcserve.
• Apply the vendor-supplied update referenced in the Arcserve Knowledge Base Article once available for your environment.
• Restrict administrative access to the UDP Console so only authorized personnel can modify activation settings.

Patch Information

Arcserve has published guidance through its support portal. Review the Arcserve Knowledge Base Article and the corresponding JVN Security Vulnerability Report for the fixed version, patch identifiers, and step-by-step upgrade instructions.

Workarounds

• Enforce outbound firewall rules that permit the UDP Console host to reach only the official Arcserve activation domain.
• Require change control review for any modification to the activation server hostname field in the console.
• Train administrators to avoid placeholder or test values in production activation configurations.

# Example egress allowlist concept for the UDP Console host
# Replace <official-arcserve-activation-host> with the value documented by Arcserve
iptables -A OUTPUT -p tcp -d <official-arcserve-activation-host> --dport 443 -j ACCEPT
iptables -A OUTPUT -p tcp --dport 443 -j REJECT