When libcurl uses libssh2 with a hashed known_hosts file, an unrelated initial entry can cause host key validation to report a key mismatch as a missing key to the CURLOPT_SSH_KEYFUNCTION callback.
known_hosts
CURLOPT_SSH_KEYFUNCTION
"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-110181.json"