redis/redis-py · error · ConnectionError

failed to fetch issuer certificate

Error message

failed to fetch issuer certificate

What it means

Error "failed to fetch issuer certificate" thrown in redis/redis-py.

Source

Thrown at redis/ocsp.py:274

        # add_certificate returns an initialized OCSPRequestBuilder
        orb = orb.add_certificate(
            cert, issuer_cert, cryptography.hazmat.primitives.hashes.SHA256()
        )
        request = orb.build()

        path = base64.b64encode(
            request.public_bytes(hazmat.primitives.serialization.Encoding.DER)
        )
        url = urljoin(server, path.decode("ascii"))
        return url

    def check_certificate(self, server, cert, issuer_url):
        """Checks the validity of an ocsp server for an issuer"""

        r = requests.get(issuer_url)
        if not r.ok:
            raise ConnectionError("failed to fetch issuer certificate")
        der = r.content
        issuer_cert = self._bin2ascii(der)

        ocsp_url = self.build_certificate_url(server, cert, issuer_cert)

        # HTTP 1.1 mandates the addition of the Host header in ocsp responses
        header = {
            "Host": urlparse(ocsp_url).netloc,
            "Content-Type": "application/ocsp-request",
        }
        r = requests.get(ocsp_url, headers=header)
        if not r.ok:
            raise ConnectionError("failed to fetch ocsp certificate")
        return _check_certificate(issuer_cert, r.content, True)

    def is_valid(self):
        """Returns the validity of the certificate wrapping our socket.
        This first retrieves for validate the certificate, issuer_url,

View on GitHub (pinned to da03cdc7e8)

When it happens

Trigger: Thrown at redis/ocsp.py:274 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of redis/redis-py@da03cdc7e8 (2026-08-04). Data as JSON: /data/errors/154f3bad6b604c01.json. Report an issue: GitHub.