A Python developer integrating a bot with the MAX messenger API faced repeated ClientConnectorCertificateError: [SSL: CERTIFICATE_VERIFY_FAILED] errors when using aiohttp. The server certificate chain is issued under the Russian Ministry of Digital Development (Минцифры) infrastructure, which is missing from standard trust stores.
Running openssl s_client revealed two certificates: the leaf for *.max.ru (valid until 2027) and the intermediate Russian Trusted Sub CA (valid until 2029) signed by Russian Trusted Root CA. Because the root is not shipped with Debian, certifi, or Windows, clients cannot complete the chain.
Broad solutions such as setting verify=False, installing the root system-wide, or appending it to certifi were rejected. These approaches either disable verification entirely or grant the intermediate authority over every domain for every client that reads the shared store, including Telegram and Anthropic connections.
The chosen implementation isolates trust to a single client. A dedicated module loads the intermediate from a local PEM file into a fresh SSLContext created with create_default_context. The flag VERIFY_X509_PARTIAL_CHAIN is set so OpenSSL can anchor on the non-self-signed intermediate. The resulting context is supplied only to the aiohttp.TCPConnector used by the MAX session.
Equivalent code works for other libraries: httpx.Client(verify=ctx), urllib.request.urlopen with the context argument, and a custom HTTPAdapter subclass for requests that mounts the context on the specific API host. On Python 3.13 the context can be passed directly as a string path; older versions require the adapter.
Risks remain limited because the file contains only one certificate and the context never leaves the MAX client. The developer records the SHA-256 fingerprint of the intermediate and re-validates it from independent networks before deployment. If the intermediate changes, only MAX requests fail while the rest of the application continues normally.
