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Sielco PolyEco Digital FM Transmitter 2.0.6 Authentication Bypass Exploit

Critical
Advisory ID
ZSL-2023-5769
Release Date
10 April 2023
Vendor
Sielco S.r.l - https://www.sielco.org
Affected Version
PolyEco1000 CPU:2.0.6 FPGA:10.19, PolyEco1000 CPU:1.9.4 FPGA:10.19, PolyEco1000 CPU:1.9.3 FPGA:10.19, PolyEco500 CPU:1.7.0 FPGA:10.16, PolyEco300 CPU:2.0.2 FPGA:10.19, PolyEco300 CPU:2.0.0 FPGA:10.19
Tested On
lwIP/2.1.1 (http://savannah.nongnu.org/projects/lwip)
Summary

PolyEco is the innovative family of high-end digital FM transmitters of Sielco. They are especially suited as high performance power system exciters or compact low-mid power transmitters. The same cabinet may in fact be fitted with 50, 100, 300, 500, 1000W power stage (PolyEco50, 100, 300, 500, 1000).

All features can be controlled via the large touch-screen display 4.3" or remotely. Many advanced features are inside by default in the basic version such as: stereo and RDS encoder, audio change-over, remote-control via LAN and SNMP, "FFT" spectral analysis of the audio sources, SFN synchronization and much more.

Description

The application suffers from an authentication bypass and account takeover/lockout vulnerability that can be triggered by directly calling the users object and effectively modifying the password of the two constants user/role (user/admin). This can be exploited by an unauthenticated adversary by issuing a single POST request to the vulnerable endpoint and gain unauthorized access to the affected device with administrative privileges.

Proof of Concept
Disclosure Timeline
26.01.2023Vulnerability discovered.
27.01.2023Contact with the vendor and CSIRT Italia.
09.04.2023No response from the vendor.
09.04.2023No response from the CSIRT team.
10.04.2023Public security advisory released.
Credits
Vulnerability discovered by Gjoko Krstic
References
Changelog
10.04.2023Initial release
03.11.2023Added reference [1], [2], [3], [4], [5], [6], [7], [8] and [9]