CVE-2025-27025: TCP Service Path Traversal Vulnerability

CVE-2025-27025 Overview

CVE-2025-27025 is a directory traversal vulnerability affecting an embedded device that exposes an HTTP service on a specific TCP port. The service protects an endpoint with Basic Authentication but improperly handles file paths supplied to the PUT and GET methods. An authenticated attacker can traverse outside the intended directory and write or read arbitrary files on the underlying file system. Because the service runs as root, written files inherit root ownership, enabling full compromise of the device. The flaw maps to [CWE-280: Improper Handling of Insufficient Permissions or Privileges].

Critical Impact
Authenticated attackers can write or read arbitrary files as root, leading to full device takeover, persistence, and exfiltration of sensitive configuration data.

Affected Products

Embedded device exposing an HTTP service on a configured TCP port (vendor and product not disclosed in NVD)
Devices using Basic Authentication for the affected endpoint
Firmware revisions implementing PUT/GET handlers without path canonicalization

Discovery Timeline

2025-07-02 - CVE-2025-27025 published to NVD
2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-27025

Vulnerability Analysis

The affected service exposes a REST-style endpoint reachable over TCP. The endpoint enforces Basic Authentication but accepts PUT and GET requests that include a file path or resource identifier. The handler concatenates the supplied path with a base directory without normalizing traversal sequences such as ../. An authenticated user can therefore reference any file on the device.

Because the HTTP daemon runs with root privileges, a PUT request writes attacker-controlled content anywhere on the file system. Targets include /etc/passwd, /etc/shadow, /etc/init.d/ scripts, SSH authorized_keys, and cron directories. A GET request returns the contents of any readable file, exposing credentials, certificates, and configuration. The flaw also undermines integrity and availability, since attackers can overwrite kernel modules or boot scripts.

Root Cause

The root cause is improper handling of privileges combined with missing path canonicalization. The endpoint trusts the authenticated user with file system operations far beyond the intended scope and fails to reject paths containing .. or absolute path prefixes. Authorization checks rely solely on Basic Authentication credentials rather than on a least-privilege model that restricts the writable directory.

Attack Vector

The attack vector is network-based and requires low-privilege Basic Authentication credentials. An attacker with valid credentials, default credentials, or credentials harvested from another source issues an HTTP PUT request whose path contains directory traversal sequences. The same mechanism applied to GET enables arbitrary file read. Tools such as curl or Postman are sufficient to deliver the payload.

The vulnerability is described in prose in the ENISA CVE-2025-27025 advisory and the CVCN CVE-2025-27025 details. No verified public exploit code is available.

Detection Methods for CVE-2025-27025

Indicators of Compromise

HTTP PUT or GET requests to the affected endpoint containing ../, %2e%2e%2f, or absolute paths such as /etc/, /root/, or /var/
Unexpected files appearing in system directories owned by root with recent modification timestamps
New or modified entries in authorized_keys, cron.d, or init scripts on the device
Outbound connections originating from the device shortly after suspicious PUT requests

Detection Strategies

Inspect web server and reverse proxy logs for Basic Authentication requests using PUT or GET against the vulnerable endpoint with traversal patterns
Deploy network signatures matching encoded traversal sequences in HTTP request URIs targeting the device's TCP port
Enable file integrity monitoring on critical system paths and alert on writes initiated by the HTTP daemon process

Monitoring Recommendations

Forward device HTTP access logs and file integrity events to a centralized SIEM for correlation
Alert on any successful Basic Authentication followed by PUT requests that exceed the expected endpoint scope
Baseline normal GET request paths and flag deviations, particularly requests referencing system configuration files

How to Mitigate CVE-2025-27025

Immediate Actions Required

Restrict network access to the affected TCP port using firewall rules so only trusted management hosts can reach the endpoint
Rotate all Basic Authentication credentials on the device and disable any default or shared accounts
Audit the file system for unauthorized files, modified init scripts, and new SSH keys, and reimage the device if tampering is found

Patch Information

No vendor patch reference is available in the NVD record at the time of publication. Consult the ENISA CVE-2025-27025 advisory and the CVCN CVE-2025-27025 details for vendor coordination updates and firmware release information.

Workarounds

Place the device behind a reverse proxy that strips or rejects URIs containing .., %2e%2e, or absolute path prefixes
Disable the PUT method at the proxy layer if the management workflow does not require file uploads
Enforce mutually authenticated TLS or VPN access in front of the management endpoint to limit exposure to authorized operators

bash

# Example nginx reverse proxy rules to block traversal and PUT on the management endpoint
location /managed-endpoint/ {
    if ($request_method = PUT) { return 405; }
    if ($request_uri ~* "(\.\./|%2e%2e|/etc/|/root/)") { return 400; }
    proxy_pass http://device.internal:PORT;
}