CVE-2026-65197: low-severity vulnerability in H3C HDM Family-A G5

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.