Error map
HTTPSConnectionPool: Max retries exceeded (SSLError) Python requests: HTTPSConnectionPool(host='api.example.com', port=443): Max retries exceeded with url: /v1 (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] ...')))
SSL / TLS · layer 2, Network
Centre: this error. First ring: errors it is linked with (9). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (9)
Cloudflare Error 1003: Direct IP access not allowed
The request went to a Cloudflare IP address directly (or with a Host header for a domain not on Cloudflare).
Cloudflare Error 1013: HTTP hostname and TLS SNI hostname mismatch
The TLS SNI (the hostname used for the certificate) differs from the HTTP Host header in the same request.
SSL: CERTIFICATE_VERIFY_FAILED / unable to get local issuer certificate
The client couldn’t verify the server’s TLS certificate chain, so it refused the HTTPS connection.
Apache: AH02240: Server should be SSL-aware but has no certificate configured / SSLCertificateFile: file '/etc/ssl/x.crt' does not exist or is empty
Apache cannot find the certificate or key file named in its configuration, or `SSLEngine on` is set without any certificate.
Apache: [ssl:warn] AH01909: example.com:443:0 server certificate does NOT include an ID which matches the server name
Apache's SSL virtual host name does not match any name inside the certificate it loads.
OpenSSL: error:1408F10B:SSL routines:ssl3_get_record:wrong version number
The peer did not answer with a TLS record — you spoke TLS to a plain HTTP/SMTP port (or the reverse), or a proxy intervened.
Python: ssl.SSLEOFError: EOF occurred in violation of protocol (_ssl.c:2396)
The server closed the TLS connection abruptly without a proper shutdown, usually because it rejected the handshake or dropped the…
Let's Encrypt: Fetching http://example.com/.well-known/acme-challenge/token: Timeout during connect (likely firewall problem)
The ACME validation server could not reach your server on port 80 within the timeout.
Let's Encrypt/CA: CAA record for example.com prevents issuance
The domain's DNS CAA records do not list the certificate authority you asked, so the CA must refuse.
Two steps away (27)
Cloudflare HTTP 530 (with Error 1016 Origin DNS error / 1033 tunnel error)
Cloudflare returns 530 together with a 1xxx error; the 1xxx code (usually 1016 or 1033) tells you the real cause.
Cloudflare Error 1000: DNS points to prohibited IP
A proxied DNS record points at a Cloudflare IP address, creating a loop.
Cloudflare Error 1001: DNS resolution error
Cloudflare received the request but the hostname isn’t set up on Cloudflare (or the domain was just added and not active yet).
fatal: unable to access 'https://…': SSL certificate problem: unable to get local issuer certificate
Git doesn’t trust the HTTPS server’s certificate — corporate proxy, self-hosted Git with an internal CA, or outdated CA bundle.
javax.net.ssl.SSLHandshakeException: PKIX path building failed: unable to find valid certification path to requested target
Java doesn’t trust the server’s certificate chain (self-signed, corporate proxy CA, or missing intermediate).
NET::ERR_CERT_AUTHORITY_INVALID (Your connection is not private)
The site’s certificate isn’t signed by a CA the browser trusts — self-signed, missing intermediates, or intercepted by a proxy.
HTTP 502 Bad Gateway
A proxy or gateway (Nginx, load balancer, CDN) got an invalid response — or no response — from the upstream server behind it.
TypeError: Failed to fetch / NetworkError when attempting to fetch resource
The browser couldn’t complete the request at the network level — CORS, DNS, offline, blocked mixed content, or the server refused…
Cloudflare Error 520: Web Server Returned an Unknown Error
Cloudflare connected to your origin, but the origin returned an empty, unknown or invalid response.
ERR_TOO_MANY_REDIRECTS with Cloudflare (Flexible SSL redirect loop)
The page redirects to itself forever — classic cause: Cloudflare SSL mode “Flexible” while the origin redirects HTTP to HTTPS.
ERR_SSL_VERSION_OR_CIPHER_MISMATCH on a Cloudflare site (certificate not issued / multi-level subdomain)
Cloudflare has no edge certificate for the hostname — the Universal SSL cert is still pending, or the hostname is a second-level…
NET::ERR_CERT_AUTHORITY_INVALID with a Cloudflare Origin Certificate (record not proxied)
Cloudflare Origin CA certificates are only trusted by Cloudflare — visitors reaching the origin directly (grey-cloud record, dire…
Apache: AH00558: apache2: Could not reliably determine the server's fully qualified domain name
A harmless startup warning: Apache has no global ServerName, so it guessed one from the host’s IP.
Firefox: Peer's Certificate has expired. Error code: SEC_ERROR_EXPIRED_CERTIFICATE
Firefox found an expired certificate in the chain presented by the server.
Firefox: Websites prove their identity via certificates — the certificate is only valid for other names. Error code: SSL_ERROR_BAD_CERT_DOMAIN
The certificate does not include the hostname you typed.
ERR_SSL_PROTOCOL_ERROR (This site can't provide a secure connection)
The browser couldn’t negotiate TLS — the server sent an invalid response, often plain HTTP on the HTTPS port.
cURL error 35: OpenSSL SSL_connect: SSL_ERROR_SYSCALL in connection to host:443
The TLS handshake failed — protocol/cipher mismatch, a proxy interfering, or the server closed the connection.
SMTP: [SSL: WRONG_VERSION_NUMBER] wrong version number — SMTP over SSL on a STARTTLS port
Your client tried to start TLS immediately on a port where the server speaks plain SMTP first (or the reverse), so the handshake…
OpenSSL: error:14094410:SSL routines:ssl3_read_bytes:sslv3 alert handshake failure (SSL alert number 40)
The server aborted the handshake with alert 40 — no acceptable parameters (cipher, signature algorithm, client certificate or SNI…
OpenSSL: SSL alert number 112 — tlsv1 unrecognized name
The server did not recognise the hostname sent in SNI and rejected the handshake (or an alert/warning is logged).
Java: javax.net.ssl.SSLHandshakeException: Received fatal alert: handshake_failure
The server rejected the Java client's TLS offer — no shared protocol/cipher, SNI issue or a required client certificate.
Cloudflare Error 1020: Access Denied
A Cloudflare firewall/WAF custom rule blocked the request — the visitor’s IP, country, user agent or request pattern matched a bl…
ssh: connect to host x port 22: Connection timed out
SSH packets get no reply — a firewall/security group drops them, the server is off, or the IP is wrong.
connect: No route to host (EHOSTUNREACH)
The destination host isn’t reachable — it’s down, on another subnet without routing, or a firewall rejects with “host unreachable…
sudo: unable to resolve host <hostname>: Name or service not known
The machine’s hostname isn’t in /etc/hosts (or DNS), so sudo prints this warning — usually after changing the hostname.
ping: google.com: Temporary failure in name resolution
The Linux host can’t resolve domain names — no working DNS server is configured or reachable.
Cloudflare Error 523: Origin is unreachable
Cloudflare can’t find a network route to your origin server — the DNS record points to a wrong/unroutable IP or the origin networ…
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