CVE-2025-48026: Mitel OpenScape Path Traversal Flaw

CVE-2025-48026 Overview

CVE-2025-48026 is a path traversal vulnerability in the WebApl component of Mitel OpenScape Xpressions through version V7R1 FR5 HF43 P913. The flaw stems from insufficient input validation in user-supplied path parameters [CWE-22]. An unauthenticated remote attacker can exploit this weakness over the network to read arbitrary files from the underlying operating system. Successful exploitation exposes sensitive configuration data, credentials, and application files that may enable follow-on attacks against the host.

Critical Impact

Unauthenticated remote attackers can traverse the file system and exfiltrate sensitive files from the underlying OS hosting Mitel OpenScape Xpressions.

Affected Products

• Mitel OpenScape Xpressions WebApl component
• Versions through V7R1 FR5 HF43 P913
• Unified messaging deployments using the affected WebApl interface

Discovery Timeline

• 2025-06-23 - CVE-2025-48026 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-48026

Vulnerability Analysis

The WebApl component of Mitel OpenScape Xpressions fails to properly validate or sanitize file path parameters supplied through HTTP requests. An attacker can submit crafted requests containing directory traversal sequences such as ../ to escape the intended web root and reference arbitrary locations on the host file system. The application then reads and returns the contents of those files to the unauthenticated requester. Because no authentication is required, the vulnerability is reachable by any actor that can connect to the WebApl HTTP service.

The EPSS score is 0.966% with a percentile of 76.672, indicating elevated relative exploitation probability compared to most published CVEs. The vulnerability impacts confidentiality only; integrity and availability of the system are not directly affected.

Root Cause

The root cause is insufficient input validation [CWE-22] on file path parameters processed by the WebApl handler. The component does not canonicalize the supplied path or restrict resolved paths to an allow-listed directory before performing file read operations.

Attack Vector

An attacker sends an HTTP request to the exposed WebApl endpoint containing directory traversal sequences in a path or filename parameter. The server resolves the path relative to a directory above the web root and returns the requested file content. Targets typically include system configuration files, application configuration containing credentials, log files, and private keys.

No verified public proof-of-concept exploit code is available. See the Mitel Security Advisory MISA-2025-0005 for vendor technical details.

Detection Methods for CVE-2025-48026

Indicators of Compromise

• HTTP requests to WebApl endpoints containing ../, ..\, %2e%2e%2f, or other encoded traversal sequences
• Unexpected access to system files such as /etc/passwd, /etc/shadow, or Windows files like win.ini and boot.ini via the WebApl service
• Anomalous outbound responses with large file payloads originating from the WebApl process

Detection Strategies

• Inspect WebApl access logs for URL-encoded or raw traversal patterns in query strings and path parameters
• Deploy web application firewall rules that block request paths containing parent directory references
• Correlate unauthenticated WebApl requests with subsequent reads of sensitive OS files

Monitoring Recommendations

• Alert on repeated 4xx and 2xx responses to malformed WebApl path requests from a single source
• Monitor file integrity tools for read access to configuration directories outside the application root
• Track outbound HTTP response sizes from the WebApl service for statistical anomalies

How to Mitigate CVE-2025-48026

Immediate Actions Required

• Apply the security update referenced in Mitel advisory MISA-2025-0005 to all OpenScape Xpressions deployments running version V7R1 FR5 HF43 P913 or earlier
• Restrict network access to the WebApl interface to trusted management networks only
• Review WebApl logs for evidence of historical path traversal exploitation

Patch Information

Mitel has published remediation guidance in the Mitel Security Advisory MISA-2025-0005. Administrators should consult the advisory for fixed versions and upgrade instructions. The full list of vendor advisories is available on the Mitel Security Advisories Overview page.

Workarounds

• Place the WebApl service behind a reverse proxy or WAF that strips or blocks traversal sequences in request paths
• Disable the WebApl component if it is not required for business operations
• Enforce network segmentation so the OpenScape Xpressions host cannot be reached directly from untrusted networks

# Example WAF rule fragment (ModSecurity) to block traversal attempts on WebApl
SecRule REQUEST_URI "@rx (\.\./|\.\.\\|%2e%2e/|%2e%2e\\)" \
    "id:1004826,phase:1,deny,status:403,msg:'Path traversal attempt against WebApl (CVE-2025-48026)'"