CVE-2025-41083: Altitude Auth Bypass Vulnerability

CVE-2025-41083 Overview

CVE-2025-41083 is a Host Header Injection vulnerability affecting Altitude Authentication Service and Altitude Communication Server version 8.5.3290.0. The vulnerability allows attackers to manipulate the Host header in HTTP requests, enabling redirection to arbitrary URLs or modification of the base URL. This can be leveraged to trick victims into sending login credentials to malicious websites controlled by the attacker.

Critical Impact

Attackers can exploit this vulnerability to redirect authenticated users to malicious endpoints, potentially capturing login credentials through phishing attacks that appear to originate from legitimate Altitude services.

Affected Products

• Altitude Authentication Service v8.5.3290.0
• Altitude Communication Server v8.5.3290.0

Discovery Timeline

• 2026-01-26 - CVE-2025-41083 published to NVD
• 2026-01-26 - Last updated in NVD database

Technical Details for CVE-2025-41083

Vulnerability Analysis

This vulnerability falls under CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), commonly known as Injection. The Altitude Authentication Service and Communication Server fail to properly validate the Host header value in incoming HTTP requests before using it to construct URLs in responses.

When an attacker sends a crafted HTTP request with a manipulated Host header, the application accepts and uses this malicious value to generate URLs within the response. This allows attackers to modify the base URL that clients use for subsequent requests, particularly affecting authentication flows where users may be directed to enter credentials.

The network-based attack vector requires user interaction, as the victim must click on a link or follow a redirect to the attacker-controlled endpoint. The vulnerability primarily impacts the confidentiality and integrity of downstream systems by enabling credential theft through sophisticated phishing scenarios.

Root Cause

The root cause stems from improper validation of the HTTP Host header before incorporating it into URL construction logic within the authentication service. The application trusts the client-supplied Host header value without sanitization, allowing arbitrary domain injection. This design flaw enables attackers to manipulate how the application generates redirect URLs and base URLs used in authentication workflows.

Attack Vector

The attack is initiated remotely over the network. An attacker crafts an HTTP request containing a malicious Host header value pointing to an attacker-controlled domain. When processed by the vulnerable Altitude server, the malicious host value is incorporated into generated URLs.

In a typical exploitation scenario:

1. The attacker sends a crafted request with a manipulated Host header (e.g., Host: attacker.com)
2. The Altitude server generates response URLs using the attacker-controlled host value
3. The victim is redirected to the attacker's domain, which may present a convincing login page
4. Credentials entered by the victim are captured by the attacker

This attack is particularly effective when combined with social engineering techniques or when targeting password reset or authentication flows.

Detection Methods for CVE-2025-41083

Indicators of Compromise

• Unusual Host header values in HTTP requests to Altitude services that don't match expected domain names
• Authentication requests containing external domains in redirect URLs or base URLs
• Web server logs showing requests with mismatched Host headers and actual server addresses
• User reports of being redirected to unfamiliar login pages after accessing Altitude services

Detection Strategies

• Implement web application firewall (WAF) rules to flag requests where the Host header doesn't match the expected server domains
• Monitor HTTP access logs for Host header anomalies and unexpected redirect patterns
• Deploy network-based detection to identify HTTP responses containing URLs pointing to unauthorized domains
• Utilize SentinelOne Singularity to detect and alert on suspicious network activity patterns associated with credential phishing attempts

Monitoring Recommendations

• Enable verbose logging on Altitude Authentication Service to capture full HTTP request headers
• Configure alerts for authentication workflow anomalies, particularly unexpected redirects
• Monitor for DNS queries to suspicious domains from systems that communicate with Altitude services
• Implement security information and event management (SIEM) correlation rules to detect potential Host header injection attempts

How to Mitigate CVE-2025-41083

Immediate Actions Required

• Implement strict Host header validation at the web server or reverse proxy level, allowing only known legitimate hostnames
• Deploy a web application firewall (WAF) with rules to block requests containing unexpected Host header values
• Educate users about the risks of clicking links in unsolicited communications and verifying URL authenticity before entering credentials
• Consider implementing additional authentication factors that are resistant to phishing attacks

Patch Information

Organizations should consult the INCIBE Security Notice for official vendor guidance and patch availability. Contact Altitude support for information on security updates addressing this vulnerability.

Workarounds

• Configure the web server or reverse proxy to enforce a whitelist of allowed Host header values
• Implement Content Security Policy (CSP) headers to restrict which domains can be used in redirects
• Use a reverse proxy to normalize and validate Host headers before forwarding requests to the Altitude services
• Enable HTTPS with strict transport security to reduce the effectiveness of man-in-the-middle attacks that could complement this vulnerability

# Example Apache configuration to restrict Host header values
# Add to virtual host configuration
<VirtualHost *:443>
    # Only accept requests with valid Host header
    ServerName altitude.example.com
    ServerAlias www.altitude.example.com
    
    # Reject requests with invalid Host headers
    RewriteEngine On
    RewriteCond %{HTTP_HOST} !^(www\.)?altitude\.example\.com$ [NC]
    RewriteRule ^ - [F]
</VirtualHost>