A flaw was found in libmodulemd. In builds with rpmio support enabled, compressed modulemd YAML is decompressed through a custom read handler that does not enforce a cumulative decompressed-size limit before parsing. An attacker who can supply a highly compressible compressed YAML file can cause excessive CPU and memory consumption, resulting in a denial of service.
Until a fix is available, avoid parsing attacker-controlled compressed module metadata in rpmio-enabled builds. Where compressed input is required, decompress outside the process under strict size quotas, or reject files whose decompressed size exceeds a conservative limit before passing data to libmodulemd. Building without rpmio support removes the affected path.