Post 43 | Security Advisory: Insecure Permissions in D-Link DCS-825L Firmware (CVE-2025-55582)

Author: Shaunak Ganorkar, Traboda Cyberlabs Pvt. Ltd.
Published: August 2025
CVE ID: CVE-2025-55582
Vendor: D-Link Systems, Inc.
Product: D-Link DCS-825L Wi-Fi Baby Camera
Firmware Affected: v1.08.01 (EU Release)
Firmware SHA-256: c11f4adddbea80fb173f7fbfc3d55fab6029af390e532261f659500eff42d0c6
Impact: Persistent Root-Level Code Execution
Severity: High
Status: Public

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Summary

The D-Link DCS-825L firmware v1.08.01 exposes a critical weakness in its filesystem permissions.
Key directories containing binaries monitored by the mydlink-watch-dog.sh script are writable without proper access controls.

An attacker with physical access, debug interface access, or the ability to modify the firmware can replace monitored binaries (such as dcp or signalc) with malicious payloads. These payloads are automatically executed as root, leading to persistent arbitrary code execution, even after reboots or factory resets.

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Vulnerability Details

• Vulnerable Script: /mydlink/mydlink-watch-dog.sh
• Writable Paths: /mydlink/ and related directories
• Monitored Binaries: /mydlink/dcp, /mydlink/signalc
• Issue: World-writable directories without authentication or permission enforcement
• Attack Type: Local / Firmware Modification
• CWE IDs:
  • CWE-732: Incorrect Permission Assignment for Critical Resource
  • CWE-269: Improper Privilege Management
  • CWE-306: Missing Authentication for Critical Function

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Proof of Concept (PoC)

Static Analysis

1. Extract the official EU firmware for v1.08.01.
2. Identify the mydlink directories as writable locations.
3. Note that the watchdog script executes binaries from these directories without verifying ownership, permissions, or integrity.

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Payload Injection

1. Create a benign ARM ELF binary payload that writes a success marker file (e.g., /tmp/poc_success).
2. Replace /mydlink/dcp with this binary in the writable partition.
3. Upon reboot or script execution, the payload is executed with root privileges.

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Attack Vector

• Physical Access: Through UART or JTAG debug interfaces.
• Firmware Modification: By unpacking and repacking the firmware image with a malicious binary.
• Exposed Debug Services: If present, they could be used to write to these directories remotely.

These methods all result in persistent code execution at the highest privilege level.

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Impact

• Persistent compromise of the camera, surviving reboots and resets.
• Botnet recruitment for distributed attacks.
• Privacy violations, enabling covert surveillance or lateral attacks in local networks.

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Severity Justification

CVSS v3.1 Base Score: 7.2 (High)
Vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L

CVSS v4.0 Base Score: 7.4 (High)
Vector: CVSS:4.0/AV:P/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

This issue stems from world-writable directories combined with privileged execution, enabling persistent code execution even after device resets or reboots.

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Recommendations

• For users:
  • Discontinue use of unsupported DCS-825L devices.
  • Replace with supported models that implement integrity validation.
• For vendors:
  • Apply proper permission enforcement on critical directories.
  • Implement code-signing and secure boot to prevent execution of tampered binaries.

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Vendor Response

• June 20, 2025: Vulnerability reported to D-Link PSIRT.
• June 21, 2025: Vendor acknowledged the report and confirmed EOL status.
• June 24, 2025: Public security announcement SAP10431 released.

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Discoverer

Shaunak Ganorkar
Traboda Cyberlabs Pvt. Ltd.

🔗 https://www.cybermaya.in
🔗 https://www.linkedin.com/in/shaunakganorkar

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Disclaimer

This research was conducted strictly for educational and responsible disclosure purposes. No unauthorized access was made to any live systems. Users are strongly advised to discontinue the use of unsupported devices.