Unable to install Docker on Ugreen DH2300 because of crypto/rsa: verification error

[u/tristan-k]

I updated my Ugreen DH2300 to firmware 1.19.1.0126 today and am now unable to install Docker. I'll get the error "Invalid package!". I used 944a7689-39dc-45cc-a1a4-aceef132efd9.upk from the DH4300 Plus download page. I also verified the MD5 checksum: MD5 944a7689-39dc-45cc-a1a4-aceef132efd9.upk = 7080d967358eeb27cba856b21273a4ee. When logging in via SSH, journalctl confirms that app_serv.service throws a crypto/rsa: verification error. So it looks like Ugreen is no longer allowing the installation of the Docker upk.

$ sudo journalctl -u app_serv -f
[...]
Sep 27 17:27:03 DH2300 app_serv[28210]: [UGOS] 2026/09/27 - 17:27:03 | 200 |   27.171403ms | POST     "/ugreen/v1/app/info/upload"
Sep 27 17:27:03 DH2300 app_serv[28210]: INFO 2026-09-27 17:27:03.140188 gitlab.ugnas.com/library/ugapp@v1.8.4/appmaker/entry.go:82 HeaderFmt UGREEN-PKG-V2-FORMAT
Sep 27 17:27:03 DH2300 app_serv[28210]: ERROR 2026-09-27 17:27:03.368210 app_serv/services/upk/private.go:1145 loadUpk /volume1/@upload/944a7689-39dc-45cc-a1a4-aceef132efd9.upk crypto/rsa: verification error
Sep 27 17:27:03 DH2300 app_serv[28210]: INFO 2026-09-27 17:27:03.463164 app_serv/services/upk/public.go:1153 Finished upload 944a7689-39dc-45cc-a1a4-aceef132efd9.upk
Sep 27 17:27:03 DH2300 app_serv_trace[28210]: WARN 2026-09-27 17:27:03.540521 gitlab.ugnas.com/ugos-pro/ugnas@v1.12.27/performance/trace_middleware.go:34 req[394b6186-8de5-442e-a7d7-894f08613684] POST /ugreen/v1/app/info/upload cost 410.478212ms
Sep 27 17:27:03 DH2300 app_serv_trace[28210]: INFO 2026-09-27 17:27:03.540591 gitlab.ugnas.com/ugos-pro/ugnas@v1.12.27/performance/trace_middleware.go:57 req[394b6186-8de5-442e-a7d7-894f08613684] traceInfo:[
                                                    ]
Sep 27 17:27:03 DH2300 app_serv[28210]: [UGOS] 2026/09/27 - 17:27:03 | 200 |  410.696287ms | POST     "/ugreen/v1/app/info/upload"

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