CVE-2025-3716: ESET Protect Information Disclosure Flaw

CVE-2025-3716 Overview

CVE-2025-3716 is a user enumeration vulnerability in ESET Protect (on-prem) that can be exploited via response timing analysis. This timing attack vulnerability (CWE-204: Observable Response Discrepancy) allows attackers on an adjacent network to determine valid usernames by measuring differences in server response times during authentication attempts.

Critical Impact

Attackers can enumerate valid user accounts through timing-based side-channel analysis, potentially enabling targeted credential attacks against confirmed accounts.

Affected Products

• ESET Protect (on-premises deployment)

Discovery Timeline

• 2026-03-30 - CVE CVE-2025-3716 published to NVD
• 2026-03-30 - Last updated in NVD database

Technical Details for CVE-2025-3716

Vulnerability Analysis

This vulnerability exploits observable response discrepancies in ESET Protect's authentication mechanism. When processing login requests, the application exhibits measurably different response times depending on whether a submitted username exists in the system or not. This timing difference creates a side-channel that attackers can leverage to enumerate valid user accounts.

The vulnerability requires adjacent network access, meaning the attacker must be positioned on the same local network segment as the ESET Protect server. No authentication or user interaction is required to exploit this flaw. While the confidentiality and integrity impacts are limited, successful exploitation can lead to availability impacts and serve as a reconnaissance step for more sophisticated attacks.

Root Cause

The root cause is CWE-204: Observable Response Discrepancy. The authentication logic performs different operations depending on whether a username exists in the database. Valid usernames may trigger additional processing steps (such as password hash retrieval and comparison), while invalid usernames return earlier in the authentication flow. This creates measurable timing differences that reveal account existence.

Attack Vector

The attack vector is Adjacent Network (AV:A), requiring the attacker to have access to the same network segment as the ESET Protect server. An attacker can systematically submit authentication requests with various usernames while precisely measuring response times. By analyzing statistical variations in response latency, they can distinguish between valid and invalid usernames. This enumerated list of valid accounts can then be used for targeted password spraying, phishing campaigns, or brute-force attacks.

The attack methodology typically involves:

1. Capturing baseline response times for known invalid usernames
2. Submitting authentication requests with potential target usernames
3. Statistically analyzing response time deltas to identify valid accounts
4. Building a list of confirmed user accounts for subsequent attacks

Detection Methods for CVE-2025-3716

Indicators of Compromise

• Multiple failed authentication attempts from a single source IP with varying usernames
• Unusual patterns of login requests occurring at precise intervals (indicative of automated timing analysis)
• Authentication requests originating from unexpected network segments or hosts
• High volume of authentication attempts against the ESET Protect management console

Detection Strategies

• Implement authentication attempt logging with detailed timestamps to identify timing-based enumeration patterns
• Configure alerting for anomalous login failure rates from single sources
• Deploy network-based intrusion detection rules to identify systematic authentication probing
• Monitor for authentication traffic patterns consistent with automated enumeration tools

Monitoring Recommendations

• Enable comprehensive authentication audit logging on ESET Protect servers
• Establish baseline authentication patterns to detect statistical anomalies
• Configure SIEM correlation rules to identify potential user enumeration campaigns
• Review authentication logs regularly for patterns of failed logins with sequential or dictionary-based usernames

How to Mitigate CVE-2025-3716

Immediate Actions Required

• Apply the latest ESET Protect updates as referenced in the ESET Product Change Logs
• Restrict network access to the ESET Protect management console to authorized administrator networks only
• Implement rate limiting on authentication endpoints to slow enumeration attempts
• Consider deploying a web application firewall (WAF) to detect and block timing-based enumeration attacks

Patch Information

ESET has addressed this vulnerability in product updates. Administrators should consult the ESET Product Change Logs for specific version information and apply the latest security updates to remediate this issue.

Workarounds

• Implement network segmentation to limit adjacent network access to the ESET Protect server
• Configure firewall rules to restrict access to the management console from authorized IP addresses only
• Deploy multi-factor authentication (MFA) to reduce the impact of successful user enumeration
• Implement account lockout policies to limit the effectiveness of subsequent credential attacks

# Network access restriction example (iptables)
# Restrict ESET Protect console access to management VLAN only
iptables -A INPUT -p tcp --dport 443 -s 10.0.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP