CVE-2025-2749: Kentico Xperience Path Traversal -- Authenticated Staging Sync File Write

Background

Kentico Xperience is an enterprise digital experience platform and CMS used by enterprises and digital agencies to build and manage websites, e-commerce platforms, and customer portals. It is deployed on Windows with IIS and SQL Server.

The Staging Sync Server feature handles content synchronisation between Kentico environments — typically staging-to-production. This server-to-server mechanism is a legitimate feature, but it exposes an additional attack surface. CISA added CVE-2025-2749 to the KEV catalogue on 2026-04-20. Path traversal in file upload functionality is a dangerous class because it can enable web shell deployment directly.

Technical Mechanism

CVE-2025-2749 is a path traversal vulnerability in Kentico Xperience’s Staging Sync Server component. The Staging Sync Server accepts file uploads as part of content synchronisation operations. Path traversal occurs when the destination path for an uploaded file is not properly sanitised, allowing ../ sequences to navigate outside the intended upload directory.

The attack requires authentication — an authenticated Kentico user with access to the Staging Sync Server. The exploitation flow is:

1. An attacker authenticates to the Kentico Xperience application with a valid user account that has access to staging synchronisation functionality
2. The attacker submits a file upload request to the Staging Sync Server endpoint with a manipulated destination path containing ../ sequences (e.g., ../../inetpub/wwwroot/kentico/cms/webshell.aspx)
3. The Staging Sync Server processes the upload and writes the file to the traversed path rather than the intended upload directory
4. The attacker writes an ASPX web shell to a web-accessible location within the IIS web root
5. The attacker accesses the web shell directly via HTTP, gaining OS command execution under the IIS application pool identity

Alternatively, the traversal could be used to overwrite configuration files, replace legitimate application files with malicious versions, or write to other sensitive locations.

Real-World Exploitation Evidence

CVE-2025-2749 was added to CISA KEV on 2026-04-20. CMS path traversal vulnerabilities follow predictable exploitation patterns:

• Web shell deployment — path traversal enabling web shell upload is one of the most operationally significant vulnerability classes; a persistent ASPX web shell provides ongoing access even after the original vulnerability is patched
• Data exfiltration — Kentico deployments hold customer data, marketing databases, and e-commerce records; initial access is commonly followed by database exfiltration
• Ransomware staging — web server compromise via CMS vulnerabilities is a common initial access pattern for ransomware groups targeting on-premises Windows/IIS infrastructure
• The authentication requirement raises the bar but does not eliminate the risk — Kentico deployments may have many user accounts, and credentials can be obtained via phishing or credential stuffing

Impact Assessment

CVE-2025-2749 affects any authenticated Kentico Xperience user with access to the Staging Sync Server, allowing them to write arbitrary files to the web server filesystem under the IIS application pool identity. The most immediate consequence is ASPX web shell deployment: a persistent web shell provides ongoing OS command execution on the Windows server that survives patching and is difficult to detect without proactive filesystem auditing. The 7.5 CVSS score reflects the authentication prerequisite; in practice, Kentico deployments often have numerous content editor and developer accounts, each a potential entry point via phishing or credential stuffing.

The business impact is concentrated in the industries that rely most heavily on enterprise CMS platforms: retail, financial services, and digital-native organisations running customer portals and e-commerce sites on Kentico. A web shell on a Kentico server provides access to the CMS database, which typically contains customer PII, transactional records, and marketing data subject to GDPR and other data protection regulations. Web server compromise also opens the path to the underlying Windows infrastructure and adjacent internal systems reachable from the IIS server. For organisations using Kentico across multiple sites or environments, the Staging Sync Server’s server-to-server trust model may allow lateral movement between staging and production environments if not properly network-segmented.

Affected Versions

Consult the Kentico Security Bulletin for precise version information and hotfix availability.

Remediation Steps

1. Apply Kentico’s security hotfix immediately
2. If patching is delayed, disable the Staging Sync Server feature if it is not actively required, or restrict access to it via IIS IP restrictions to only known staging/synchronisation server IP addresses
3. Search the Kentico web root and related directories for unexpected ASPX files that may have been placed via path traversal exploitation:

   Get-ChildItem -Path "C:\inetpub\wwwroot" -Recurse -Include "*.aspx" |
     Where-Object {$_.LastWriteTime -gt (Get-Date).AddDays(-30)} |
     Select-Object FullName, LastWriteTime

4. Review IIS access logs for unexpected HTTP requests to ASPX files outside the normal Kentico application paths
5. Rotate all Kentico database credentials and integration credentials
6. Review Kentico CMS user accounts for unexpected additions or privilege escalations
7. Verify IIS application pool identity permissions — apply principle of least privilege
8. Enable file integrity monitoring on the Kentico web root and application directories

Detection Guidance

IIS access logs (W3SVC log files) — look for:

• POST requests to Staging Sync Server endpoints with path values containing ../ or %2e%2e%2f
• Access to ASPX files in unexpected locations (outside normal Kentico application paths) following the upload window
• HTTP 200 responses to requests for newly created files in non-CMS directories

Kentico CMS audit logs:

• Staging synchronisation events from unexpected source IP addresses
• File synchronisation operations with destination paths containing traversal sequences

SIEM query example (Splunk):

index=iis_logs cs_host="*kentico*" OR cs_host="*xperience*"
| where cs_method="POST" AND (cs_uri_stem like "*/Staging*" OR cs_uri_stem like "*/Sync*")
| eval traversal=if(match(cs_post_body, "\.\.[\\/]") OR match(cs_uri_query, "\.\."), "YES", "NO")
| where traversal="YES"
| stats count by c_ip, cs_uri_stem, sc_status

Windows File Auditing:

• Enable object access auditing on the Kentico web root
• Alert on file creation events in IIS web directories outside expected Kentico paths

Timeline

References

• NVD — CVE-2025-2749
• CISA KEV — CVE-2025-2749
• MITRE CVE — CVE-2025-2749