Unauthenticated RCE in Motorola's MR2600 Router
A security researcher embarked on a mission to find Remote Code Execution (RCE) vulnerabilities in routers, ultimately uncovering an unauthenticated RCE in Motorola's MR2600. The detailed technical breakdown reveals multiple logical flaws in firmware validation and authentication mechanisms. This saga highlights prevalent security shortcomings in consumer network hardware and the frustrating labyrinth of vendor support for end-of-life products.
The Lowdown
On his self-proclaimed quest to find at least one Remote Code Execution (RCE) vulnerability per router vendor, MrBruh turned his attention to the Motorola MR2600. This deep dive into a Wi-Fi 5 router, whose last firmware update was in mid-2024, exposed critical vulnerabilities that allow for unauthenticated remote code execution.
- Firmware Acquisition Challenges: Unlike most Motorola routers, the MR2600's firmware was publicly available, providing the necessary starting point for analysis.
- Malicious Firmware Upload Flaw: The
fwuploadendpoint, intended for legitimate firmware upgrades, contained a parsing error. It incorrectly validated the multipart form boundary instead of the actual firmware data, meaning any legitimate upload would fail. Attackers, however, could bypass this by sending raw firmware data without a multipart boundary. - Authentication Bypass (Upload): While an authentication check existed for the firmware upload, it only triggered after the malicious firmware was written to
/tmp/firmware.img. Crucially, the file was not deleted if authentication failed. - Flashing Vulnerability: The
LoadFirmwareValidationSOAP action, which triggers the firmware flash, lacked cryptographic signing, meaning any validly structured (though potentially malicious) firmware could be accepted. - Authentication Bypass (Flashing): A severe logical flaw in the authentication function allowed bypassing checks. The system used substring matching for allowlisted paths but an exact match for the denylisted
/WEBCGI1/path. Appending an allowlisted string as an HTTP parameter (e.g.,?Login.html) to/WEBCGI1/allowed unauthorized access to the flashing function. - Complete Exploit Chain: The exploit involves uploading malicious firmware via the
fwupload.cgiendpoint, then triggering theLoadFirmwareValidationfunction with the authentication bypass, leading to the router flashing the new firmware and rebooting. - Exploitability: The vulnerability is exploitable by anyone on the local network (LAN) without authentication. Furthermore, with remote management enabled, the exploit is accessible from the public internet, with Shodan identifying at least 41 exposed MR2600 routers.
- Previous Discoveries & Vendor Non-Response: The author noted that Exodus Intelligence had previously found other RCEs and authentication bypasses for the same router, though details were paywalled. MrBruh's attempt to report the vulnerability to Motorola was met with both Motorola Mobility and Motorola Solutions disavowing responsibility for the End-of-Life (EOL) product, leading to public disclosure.
This detailed account underscores not only the technical ingenuity in discovering such flaws but also the significant challenges security researchers face when dealing with product manufacturers, particularly for EOL devices, ultimately leaving users vulnerable.