H3C HDM Family-A verifies the RSA signature of a firmware image against a public key it reads from the mutable file /conf/public.pem. That file is writable by an authenticated Redfish client through the UpdateService.UploadSignKey action, which stores the uploaded body verbatim after validating only that the multipart filename ends in .pem. An administrator, or any account with firmware-update privilege, can therefore replace the trust anchor with their own key, sign a malicious image with the matching private key, and have it pass verification. Family-A has no hardware root-of-trust (no PFR) to catch the substituted key.
This was observed on H3C HDM Family-A G5 HDM 6.14.01. H3C HDM Family-A G3/G5 builds carrying the Redfish/DRE update tree appear to be affected. HDM2 uses a different update path and is not covered by this finding.