CVE-2025-27932 Overview
CVE-2025-27932 is a path traversal vulnerability [CWE-22] affecting the USB storage file-sharing function of the HGW-BL1500HM home gateway router. The flaw resides in the file deletion process, where the device fails to properly restrict pathnames to the intended directory. An authenticated attacker on the network can craft a request containing traversal sequences to delete files outside the USB storage boundary. Successful exploitation enables arbitrary file deletion on the device or a denial of service (DoS) condition. The vulnerability affects HGW-BL1500HM firmware version 002.002.003 and earlier.
Critical Impact
An authenticated network attacker can delete arbitrary files on the device, potentially rendering the home gateway inoperable and triggering a denial of service.
Affected Products
- HGW-BL1500HM firmware version 002.002.003 and earlier
- USB storage file-sharing function on the affected device
- Networks relying on the HGW-BL1500HM as the home gateway
Discovery Timeline
- 2025-03-28 - CVE-2025-27932 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-27932
Vulnerability Analysis
The vulnerability stems from improper limitation of a pathname to a restricted directory within the USB storage file-sharing function. When the device processes a file deletion request, it accepts user-supplied filename input without sanitizing directory traversal sequences such as ../. The deletion routine then resolves the manipulated path outside the intended USB storage root and removes the target file. Because the affected function operates on shared storage exposed over the network, an attacker with valid low-privilege credentials can reach the vulnerable code path remotely. The impact is integrity and availability loss, with no direct confidentiality exposure indicated by the advisory.
Root Cause
The root cause is missing or insufficient canonicalization and validation of file path parameters supplied to the deletion handler. The handler trusts the client-supplied path and does not enforce that the resolved path remains within the USB storage directory. This is a classic CWE-22 path traversal weakness applied to a destructive operation.
Attack Vector
The attack is conducted over the network against the file-sharing interface of the gateway. The attacker requires low-level credentials to authenticate, but no user interaction is needed. By submitting a delete request with a relative path containing traversal sequences, the attacker forces the device to remove files outside the shared directory. Repeated deletion of configuration or runtime files can drive the device into a denial of service state.
No public proof-of-concept exploit is referenced in the advisories. Refer to the JVN Security Advisory JVN04278547 and the KDDI Technical Document Appendix L2 for vendor-provided technical details.
Detection Methods for CVE-2025-27932
Indicators of Compromise
- File deletion requests to the USB storage file-sharing endpoint containing traversal sequences such as ../ or encoded variants like %2e%2e%2f.
- Unexpected disappearance of system, configuration, or user files on the HGW-BL1500HM device.
- Repeated authenticated sessions originating from unusual internal hosts targeting the file-sharing service.
Detection Strategies
- Inspect gateway access logs for file-sharing API calls containing directory traversal patterns in filename or path parameters.
- Alert on bursts of file deletion operations against the USB storage service from a single source address.
- Correlate authentication events for the gateway management plane with subsequent file-sharing activity to identify abuse of low-privilege accounts.
Monitoring Recommendations
- Forward HGW-BL1500HM syslog output to a centralized log platform and retain file-sharing activity for review.
- Monitor device availability and integrity of attached USB storage for unplanned file removals or service restarts.
- Track firmware version inventory to confirm that no device remains on 002.002.003 or earlier.
How to Mitigate CVE-2025-27932
Immediate Actions Required
- Update the HGW-BL1500HM firmware to the fixed version released by the vendor as referenced in the JVN advisory.
- Restrict access to the USB storage file-sharing function to trusted users and segments only.
- Rotate credentials for any account authorized to use the file-sharing service.
Patch Information
The vendor has published remediation guidance through the KDDI Technical Document Appendix L2 and the JVN Security Advisory JVN04278547. Operators should follow the vendor's firmware update procedure to install the version that addresses CVE-2025-27932. Confirm successful update by validating the running firmware version is later than 002.002.003.
Workarounds
- Disable the USB storage file-sharing function until the firmware update can be applied.
- Remove the USB storage device from the gateway in environments where file-sharing is not required.
- Apply network segmentation to ensure only authorized hosts can reach the gateway management and file-sharing interfaces.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
