Post 42 | Security Advisory: Persistent Privilege Escalation in D-Link DCS-825L Firmware (CVE-2025-55581)

Author: Shaunak Ganorkar, Traboda Cyberlabs Pvt. Ltd.
Published: August 2025
CVE ID: CVE-2025-55581
Vendor: D-Link Systems, Inc.
Product: D-Link DCS-825L Wi-Fi Baby Camera
Firmware Affected: v1.08.01 and possibly prior
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 contains a critical flaw in the watchdog script mydlink-watch-dog.sh.
This script continuously monitors and automatically restarts two binaries — dcp and signalc.

Because it performs no integrity checks, signature validation, or permission verification, an attacker with filesystem access (via UART, firmware modification, or debug interfaces) can replace these binaries with malicious payloads.

Once replaced, the watchdog script respawns the malicious binaries with root privileges, resulting in persistent arbitrary code execution even after reboots.

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Vulnerability Details

• Vulnerable Script: /mydlink/mydlink-watch-dog.sh
• Monitored Binaries: /mydlink/dcp, /mydlink/signalc
• Issue: No cryptographic or permission validation before execution
• Attack Type: Local / Firmware Modification
• CWE IDs:
  • CWE-306: Missing Authentication for Critical Function
  • CWE-269: Improper Privilege Management
  • CWE-840: Business Logic Errors

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Proof of Concept (PoC)

Steps

1. Extract the D-Link DCS-825L v1.08.01 firmware.
2. Replace /mydlink/dcp with a custom ARM binary (benign PoC payload).
3. Repack and deploy the firmware, or gain shell access to update the file directly.
4. Observe that the watchdog script respawns the payload with root privileges continuously.

Validation

• Using QEMU-based emulation, a benign payload was executed to create a /tmp/poc_success file, proving arbitrary code execution.
• No integrity validation or sandboxing prevented the execution.

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Attack Vector

An attacker needs:

• Local access (physical UART/debug access) or
• Firmware modification capability (e.g., insecure update processes).

With this, they can:

• Inject a malicious payload into dcp or signalc.
• Gain persistent root-level control over the camera, surviving reboots.

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Impact

• Persistent compromise of the device even after factory reset or power cycles.
• Botnet risk: Vulnerable devices could be absorbed into IoT botnets.
• Privacy breach: Cameras could be covertly used for surveillance.

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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

While the attack requires local or firmware-level access, the ability to achieve persistent root-level execution makes the vulnerability highly impactful for IoT exploitation and persistence.

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Recommendations

• For users:
  • Immediately disconnect or replace unsupported DCS-825L devices.
  • Avoid using EOL IoT devices in production or sensitive environments.
• For vendors:
  • Enforce integrity and signature checks before respawning binaries.
  • Implement secure boot and code-signing mechanisms for critical scripts.

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Vendor Response

• June 20, 2025: Vulnerability reported to D-Link PSIRT.
• June 21, 2025: Vendor acknowledged the issue and confirmed the device is End-of-Life (EOL) and will not be patched.
• June 24, 2025: Public security advisory SAP10431 published.

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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.