Error map
ERR_SSL_KEY_USAGE_INCOMPATIBLE Chrome: ERR_SSL_KEY_USAGE_INCOMPATIBLE — the certificate's key usage doesn't allow the negotiated cipher
SSL / TLS · layer 2, Network
Centre: this error. First ring: errors it is linked with (7). 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 (7)
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.
Nginx: [emerg] SSL_CTX_use_PrivateKey_file("/etc/ssl/server.key") failed (SSL: error:0B080074:x509 certificate routines:X509_check_private_key:key values mismatch)
The private key does not belong to the certificate configured in the server.
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.
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.
OpenSSL: error:0A00018E:SSL routines::ca md too weak / error:140AB18F:SSL routines:SSL_CTX_use_certificate:ee key too small
OpenSSL's security level rejected a certificate signed with a weak hash (MD5/SHA-1) or with a small key (RSA < 2048).
Chrome: ERR_HTTP2_INADEQUATE_TRANSPORT_SECURITY — HTTP/2 requires a modern TLS cipher
The server speaks HTTP/2 but negotiated a TLS version or cipher that HTTP/2 forbids (blocklisted ciphers or TLS below 1.2).
Two steps away (21)
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…
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Nginx (or another server) can’t listen on the port because another process already holds it — often Apache, another Nginx, or a s…
Nginx: upstream timed out (110: Connection timed out) while reading response header from upstream
Nginx waited longer than proxy_read_timeout (60 s default) for the backend (app server, PHP-FPM) to respond, then returned 504.
Nginx: nginx: [emerg] unknown directive "x" in /etc/nginx/sites-enabled/x:12 — configuration file test failed
Nginx found a directive it doesn’t know — a typo, a missing semicolon on the previous line, a directive from a module that isn’t…
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.
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…
Error: error:0308010C:digital envelope routines::unsupported
An old build tool (webpack 4, old react-scripts) uses a hash algorithm that OpenSSL 3 in Node 17+ disables.
OpenSSL: unable to load certificate / PEM routines:get_name:no start line (key values mismatch)
OpenSSL (or Nginx/Apache) couldn’t read the certificate or key — wrong file format, wrong file, or the key doesn’t match the cert…
OpenSSL: error:num=20:unable to get local issuer certificate / SSL: CERTIFICATE_VERIFY_FAILED
The client could not build a chain from the server's certificate to a CA it trusts — the issuer is missing locally or the server…
Chrome: This site can’t provide a secure connection — uses an unsupported protocol. ERR_SSL_VERSION_OR_CIPHER_MISMATCH
The browser and the server could not agree on a TLS version or cipher — the server is too old or misconfigured, or the browser is.
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…
Nginx: [emerg] no "ssl_certificate" is defined for the "listen ... ssl" directive in /etc/nginx/sites-enabled/default:3
A server block listens with `ssl` but has no `ssl_certificate` and `ssl_certificate_key`.
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