CVE-2025-2746: Kentico Xperience Auth Bypass Vulnerability

CVE-2025-2746 Overview

CVE-2025-2746 is a critical authentication bypass vulnerability affecting Kentico Xperience, a popular content management system (CMS) and digital experience platform. The vulnerability exists in the Staging Sync Server component's digest authentication mechanism, specifically in how it handles empty SHA1 usernames during password validation. This flaw allows unauthenticated attackers to bypass authentication entirely and gain administrative control over the affected Kentico Xperience installation.

The vulnerability has been added to CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating active exploitation in the wild. Organizations running vulnerable versions of Kentico Xperience should treat remediation as an urgent priority.

Critical Impact

This authentication bypass vulnerability allows unauthenticated remote attackers to gain administrative access to Kentico Xperience installations, potentially leading to complete system compromise, data theft, and malicious content injection.

Affected Products

• Kentico Xperience through version 13.0.172

Discovery Timeline

• 2025-03-24 - CVE CVE-2025-2746 published to NVD
• 2025-11-06 - Last updated in NVD database

Technical Details for CVE-2025-2746

Vulnerability Analysis

This vulnerability is classified as CWE-288 (Authentication Bypass Using an Alternate Path or Channel). The flaw resides in Kentico Xperience's Staging Sync Server, which provides content synchronization capabilities between staging and production environments. The authentication mechanism implements digest authentication but fails to properly validate scenarios where empty SHA1 username values are submitted.

When processing authentication requests, the vulnerable code path does not adequately verify that valid credentials have been provided before granting access. An attacker can exploit this weakness by crafting malicious requests that trigger the flawed password handling logic, effectively bypassing the authentication layer entirely.

Successful exploitation grants attackers administrative privileges over the CMS, enabling them to create, modify, or delete content, access sensitive configuration data, upload malicious files, and potentially achieve remote code execution through administrative functionality. The network-accessible nature of this vulnerability combined with no required user interaction or privileges makes it particularly dangerous.

Root Cause

The root cause lies in improper input validation within the Staging Sync Server's digest authentication implementation. When processing authentication credentials, the system fails to properly handle edge cases where the SHA1-hashed username field is empty or malformed. Instead of rejecting these malformed authentication attempts, the vulnerable code path permits access, treating the request as authenticated.

This type of authentication bypass often occurs when developers implement custom authentication schemes without accounting for all possible input states, particularly null, empty, or specially-crafted values that can trigger unintended code paths.

Attack Vector

The attack is network-based and can be executed remotely without any user interaction or prior authentication. Attackers target the Staging Sync Server endpoint, which is typically exposed on the network for content synchronization purposes. By sending specially crafted HTTP requests with manipulated digest authentication headers containing empty SHA1 username values, attackers can bypass authentication controls.

Once authentication is bypassed, the attacker gains access to administrative staging functionality, which can be leveraged to:

1. Synchronize malicious content to production environments
2. Access sensitive administrative objects and configuration data
3. Escalate the attack to achieve remote code execution through administrative features
4. Exfiltrate sensitive information from the CMS database

Research from Watchtowr Labs documented a complete pre-authentication remote code execution chain leveraging this and related vulnerabilities in Kentico Xperience. For detailed technical analysis, refer to the Watchtowr CMS RCE Analysis.

Detection Methods for CVE-2025-2746

Indicators of Compromise

• Unusual authentication attempts to the Staging Sync Server endpoint with malformed or empty digest authentication headers
• Unexpected administrative actions or content modifications without corresponding legitimate user sessions
• Access logs showing requests to staging synchronization endpoints from unexpected IP addresses or at unusual times
• Evidence of unauthorized content synchronization between staging and production environments

Detection Strategies

• Monitor web server access logs for requests to Staging Sync Server endpoints, particularly those with unusual or malformed Authorization headers
• Implement Web Application Firewall (WAF) rules to detect and block requests with empty or invalid digest authentication parameters
• Review Kentico Xperience audit logs for administrative actions that do not correlate with legitimate user activity
• Deploy network intrusion detection signatures targeting exploitation patterns associated with CVE-2025-2746

Monitoring Recommendations

• Enable verbose logging on the Staging Sync Server component to capture all authentication attempts
• Configure alerting for failed authentication attempts followed by successful access without valid credentials
• Monitor for signs of unauthorized content changes or synchronization activity
• Implement file integrity monitoring on Kentico Xperience installation directories to detect unauthorized modifications

How to Mitigate CVE-2025-2746

Immediate Actions Required

• Apply the latest security hotfix from Kentico immediately, available from the Kentico Hotfix Downloads page
• If immediate patching is not possible, disable or restrict network access to the Staging Sync Server functionality
• Review audit logs for signs of prior exploitation and investigate any suspicious administrative activity
• Consider temporarily taking affected systems offline if active exploitation is suspected

Patch Information

Kentico has released security hotfixes to address this vulnerability. Organizations should download and apply the appropriate hotfix for their Kentico Xperience version from the official Kentico Hotfix Downloads portal. Given that this vulnerability is actively exploited and listed in CISA's KEV catalog, patching should be treated as an emergency priority.

For additional technical details and proof-of-concept information, refer to the GitHub Auth Bypass PoC and the VulnCheck Advisory on Kentico.

Workarounds

• Disable the Staging Sync Server functionality if not actively required for business operations
• Implement network-level access controls (firewall rules, VPN requirements) to restrict access to Staging Sync Server endpoints to trusted IP addresses only
• Place the Kentico Xperience installation behind a reverse proxy or WAF configured to block malformed authentication requests
• Enable additional authentication layers such as client certificate requirements or IP whitelisting for staging synchronization endpoints

# Example: Restrict access to Staging Sync Server via IIS URL Rewrite
# Add to web.config within the <system.webServer> section
# This blocks external access to the staging synchronization endpoint

# In IIS, configure IP address restrictions for the staging endpoint:
# 1. Open IIS Manager
# 2. Navigate to the Kentico site
# 3. Select "IP Address and Domain Restrictions"
# 4. Add deny rules for all external IPs accessing /CMSPages/Staging/