CVE-2024-1104: Areal-topkapi Webserv2 Auth Bypass Issue

CVE-2024-1104 Overview

CVE-2024-1104 affects Areal Topkapi Webserv2, a web service component used in industrial supervision and SCADA environments. An unauthenticated remote attacker can bypass the brute force prevention mechanism and disrupt the web service for all users. The flaw maps to [CWE-307: Improper Restriction of Excessive Authentication Attempts]. Exploitation requires no authentication, no user interaction, and only network access to the target web service. The result is a denial-of-service condition that affects every legitimate user of the service.

Critical Impact

Unauthenticated attackers can remotely disrupt the Webserv2 service availability by abusing the broken brute force prevention logic, blocking all legitimate users from accessing the web interface.

Affected Products

• Areal Topkapi Webserv2 (all versions prior to the vendor-supplied fix)
• Deployments exposing Webserv2 to untrusted networks
• Industrial environments relying on Webserv2 for operator web access

Discovery Timeline

• 2024-02-22 - CVE-2024-1104 published to NVD
• 2025-05-06 - Last updated in NVD database

Technical Details for CVE-2024-1104

Vulnerability Analysis

The vulnerability resides in the brute force prevention logic of Webserv2. The mechanism is intended to throttle or block repeated authentication attempts against the web service. An unauthenticated attacker can bypass this control and trigger conditions that disturb the web service for all users.

The attack vector is network-based with low complexity and requires no privileges or user interaction. The impact is restricted to availability, with confidentiality and integrity unaffected. Because the bypass affects shared protection logic, a single attacker can deny service to every user of the deployment.

Root Cause

The root cause is improper restriction of excessive authentication attempts, classified under [CWE-307]. The brute force prevention component fails to correctly enforce its rate-limiting or lockout state against attacker-controlled inputs. An attacker can manipulate request patterns or identifiers so the protection mechanism either does not trigger when it should, or triggers in a way that locks out legitimate users.

Attack Vector

An unauthenticated remote attacker sends crafted authentication-related requests to the exposed Webserv2 endpoint. By abusing the flawed protection logic, the attacker forces the service into a state that prevents legitimate access. No credentials, tokens, or prior foothold are required. Public-facing or weakly segmented Webserv2 instances are most exposed.

No verified public proof-of-concept is available. Refer to the Areal Topkapi Security Bulletins for technical specifics released by the vendor.

Detection Methods for CVE-2024-1104

Indicators of Compromise

• Repeated failed authentication requests against Webserv2 endpoints from a single or rotating set of source IPs
• Sudden inability of legitimate users to authenticate while the underlying service process remains running
• Spikes in HTTP requests to login or session endpoints without successful authentications
• Lockout or throttling state applying to broad user populations rather than individual accounts

Detection Strategies

• Monitor web server access logs for high-volume authentication request patterns to Webserv2 endpoints
• Correlate authentication failures with user-reported service unavailability
• Alert on anomalous ratios of failed logins to unique source identifiers
• Inspect reverse proxy or WAF telemetry for repeated POSTs to authentication URIs from untrusted networks

Monitoring Recommendations

• Establish baselines for normal authentication traffic volume to Webserv2 and alert on deviations
• Track availability metrics of the Webserv2 service from synthetic monitoring probes
• Forward Webserv2 and upstream proxy logs to a centralized analytics platform for correlation
• Review SIEM rules for [CWE-307] patterns covering authentication abuse and lockout floods

How to Mitigate CVE-2024-1104

Immediate Actions Required

• Apply the vendor-supplied update referenced in the Areal Topkapi Security Bulletins as soon as it is available for your version
• Restrict network exposure of Webserv2 to trusted management networks and VPN users only
• Place Webserv2 behind a reverse proxy or WAF that enforces independent rate limiting on authentication endpoints
• Monitor authentication endpoints for abuse patterns and alert security operations on anomalies

Patch Information

Areal Topkapi distributes fixes and version guidance through its security bulletin portal. Consult the Areal Topkapi Security Bulletins for the specific patched build addressing CVE-2024-1104 and follow the vendor's upgrade procedure for Webserv2.

Workarounds

• Enforce IP allowlisting at the network perimeter so only authorized operator workstations can reach Webserv2
• Deploy upstream rate limiting or connection throttling on authentication URIs to absorb abusive traffic
• Require VPN or zero-trust network access in front of Webserv2 to remove direct internet exposure
• Segment Webserv2 from general corporate networks to limit attacker reachability

# Example: nginx reverse proxy rate limiting for Webserv2 authentication endpoint
http {
    limit_req_zone $binary_remote_addr zone=webserv2_auth:10m rate=5r/m;

    server {
        listen 443 ssl;
        server_name webserv2.example.local;

        location /login {
            limit_req zone=webserv2_auth burst=5 nodelay;
            limit_req_status 429;
            proxy_pass http://webserv2_backend;
        }

        location / {
            allow 10.0.0.0/8;
            deny all;
            proxy_pass http://webserv2_backend;
        }
    }
}