“Connection reset by peer” is a TCP connection failure, not a diagnosis of a particular WordPress bug. The remote endpoint or an intermediary closed the connection. Find the failed hop first—browser to web server, Nginx to PHP-FPM, or WordPress/PHP to an external HTTPS service—then use the matching logs, tests and configuration checks. The sequence below isolates the layer without randomly reinstalling WordPress.
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What “connection reset by peer” means in WordPress
TCP uses a reset (RST) to terminate a connection abruptly. “Peer” means the other endpoint from the point of view of the process reporting the error; it might be your origin server, PHP-FPM, a reverse proxy, a firewall, or a remote API. The message therefore tells you where a connection stopped, but not why.
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- Browser to origin: a visitor, administrator or editor cannot load a page, login form or REST request.
- Web server to PHP: Nginx or Apache connects to PHP-FPM and the upstream process closes before returning response headers.
- WordPress/PHP to an external service: a plugin, update checker, webhook or API client fails during an outbound TLS connection.
- Plugin or theme request: a particular admin screen, upload, comment action or integration triggers a failing service.
WordPress support describes cURL error 35 as usually server-related and advises checking the host, Cloudflare, firewall rules and caching. That guidance is useful, but it does not identify which component reset your connection. Treat the exact error text and timestamp as your starting evidence.
Identify the failing hop before changing anything
Use the wording, direction and affected URL to classify the problem. Do not assume that every reset is an application or plugin defect.
| Observed symptom | Most likely layer | First targeted action |
|---|---|---|
cURL error 35: OpenSSL SSL_connect: Connection reset by peer during an API call |
PHP cURL/OpenSSL, an outbound proxy or firewall, or the remote API path | Run a verbose cURL test from the server, check PHP and cURL versions, and ask the host to trace outbound TLS. |
recv() failed (104: Connection reset by peer) while reading response header from upstream |
PHP-FPM/FastCGI or another Nginx upstream | Check PHP-FPM health and fatal-error logs, the socket or upstream address, process limits, timeouts and proxy TLS settings. |
| Only wp-admin, uploads, comments or one integration fails | A plugin, theme or that integration’s external service | Reproduce the action with integrations isolated; deactivate plugins one at a time in a maintenance window. |
| The same site works in development but resets in production | Production hosting, proxy, firewall, TLS, DNS or resource conditions | Compare the two environments and use production timestamps and logs rather than treating it as a WordPress-core bug. |
| Visitors see a browser TLS or connection failure on many routes | DNS, certificate, reverse proxy, firewall or protocol handling between client and origin | Check the proxy and certificate path, then test the origin directly where your hosting setup permits it. |
Five-minute evidence checklist
Capture evidence while the failure is reproducible. A later, vague report such as “the site went down” is rarely enough for a host to identify the resetter.
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- Save the exact message. Copy the complete browser, WordPress Site Health, plugin or server error. Record the HTTP status if one is shown, the request path and the cURL error number.
- Record the time and frequency. Include the timezone, whether every attempt fails, and whether only one route or user action is affected.
- Note both directions. State whether a browser was connecting to WordPress or WordPress was calling an external service. Include client and server IP addresses when available.
- List recent changes. Record WordPress, PHP, plugin, theme, Nginx, firewall, CDN, certificate and hosting changes made before the first reset.
- Preserve logs before rotation. Export the relevant Nginx or Apache, PHP, PHP-FPM, WordPress debug, WAF and firewall lines for the same minute.
Do not repeatedly retry a failing write operation such as a payment webhook or content update until you know whether it may have completed server-side. A reset means the connection ended; it does not by itself prove that the remote action was rolled back.
Step-by-step troubleshooting procedure
1. Read every log at the same timestamp
Start with the web-server error log, then correlate the request in PHP and PHP-FPM logs. If the request came from a plugin, inspect WordPress debug logging and that service’s request log. Finally check WAF, firewall, reverse-proxy and hosting logs. Matching timestamps distinguish “Nginx could not read PHP’s headers” from “the remote API rejected an outbound TLS handshake.”
Look for a PHP fatal error, worker termination, out-of-memory event, exhausted process pool, upstream timeout, rejected TLS handshake, blocked source address or configuration reload immediately before the reset. A single line without its surrounding entries can hide the actual cause.
2. Test the endpoint outside WordPress
For an outbound failure, run the test from the same server and account that PHP uses, not only from your laptop:
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Where the service supports it, compare protocol handling:
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Use the exact hostname and path that failed. The verbose output shows DNS resolution, address selection, TCP connection, TLS negotiation and response headers. A reset during SSL_connect points to the TLS path; a successful TLS handshake followed by a reset while reading the response points later in the chain.
Run the test with the server’s configured proxy environment, if any, and then with that proxy path examined by the host. Do not disable certificate verification as a “fix”: that can hide a certificate or interception problem and leaves the connection unsafe. If command-line cURL fails outside WordPress in the same way, investigate the server, proxy, firewall or remote service before changing WordPress code.
3. Correct an outdated outbound TLS stack
Wordfence support notes that cURL error 35 appears when a site cannot connect to its servers using SSL and can result from older cURL or proxying. Update PHP and the system cURL/OpenSSL packages through your host’s supported method, then retest. Confirm the PHP version used by web requests, because the command-line PHP binary and PHP-FPM pool can load different libraries.
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After an update, verify that the server still trusts current certificate authorities and that the configured proxy permits the destination and TLS version. If you do not control package versions, give the host the cURL verbose output and the PHP-FPM pool identity so it can check the runtime actually serving WordPress.
4. Isolate plugins and themes safely
If the reset occurs only in wp-admin, uploads, comments or one integration, first reproduce it with that action isolated. Plesk identifies corrupted WordPress plugins as a possible cause and recommends deactivating plugins one by one, then reinstalling or deleting the identified plugin.
- Schedule a maintenance window and make a current backup.
- Disable one plugin, reproduce the exact failing request, and record the result.
- Continue one at a time until the reset disappears; reactivate unaffected plugins after each test where practical.
- Switch temporarily to a maintained default theme if the failure is front-end or theme-admin specific.
- Reinstall the identified plugin from a trusted package or remove it and contact its maintainer with the timestamp and logs.
If you cannot access wp-admin, use your host’s control panel or file manager to rename the plugins directory, or ask the host to perform the isolation. Restore the original directory name after testing and avoid leaving a production site in a partially disabled state.
5. Repair the Nginx–PHP-FPM boundary
The message recv() failed (104: Connection reset by peer) while reading response header from upstream means Nginx was reading from an upstream and that upstream closed the connection before returning complete headers. In a WordPress stack, the upstream is commonly PHP-FPM, although it can be another proxy or application server.
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- Check that PHP-FPM processes are running and that the pool has not hit its worker, request or file-descriptor limits.
- Read PHP-FPM and PHP fatal-error logs for crashes, memory exhaustion and forced terminations at the same time.
- Compare Nginx fastcgi timeouts with the actual execution time of the failing request; raising a timeout cannot repair a worker that is crashing.
- Check recent PHP-version or extension changes, because a fatal error or incompatible extension can terminate the upstream before headers.
A WordPress support case documents this exact Nginx error while reading a PHP 8.2-FPM response header. The important clue is the boundary: investigate PHP-FPM health and its logs, not only browser cache or WordPress settings.
6. Check reverse-proxy SSL forwarding
A reverse proxy must pass the intended TLS information when it connects to an HTTPS upstream. Plesk documents resets when Nginx reverse proxying is used without correctly passing SSL and states proxy_ssl_server_name on; in Additional nginx directives as the remedy for that configuration. Apply such a change only when your topology requires it, validate the Nginx configuration, and reload during a controlled window.
Also verify which layer terminates TLS, whether the upstream expects the original hostname through SNI, and whether a firewall permits the proxy-to-origin connection. A browser-side reset and an origin-side reset can look similar while requiring changes in different machines.
7. Compare production with a known-good environment
When development works but production resets, build a side-by-side comparison rather than copying random settings. Record:
- PHP and cURL/OpenSSL versions and loaded extensions;
- Nginx or Apache version, PHP handler, socket or upstream address and worker limits;
- DNS records, certificate chain, TLS termination point and HTTP protocol settings;
- outbound proxy, firewall and WAF rules;
- plugin and theme versions, environment variables and integration endpoints;
- CPU, memory, process, file-descriptor and request-timeout conditions at the failure time.
Change one variable at a time and keep a rollback point. If production is managed, ask the provider to perform the comparison because it may control the proxy, kernel, firewall or PHP service that WordPress cannot inspect.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Targeted fixes by error pattern
“cURL error 35” during an API call
Start at the outbound path: test the destination from the server, inspect verbose TLS output, update the PHP/cURL stack, and check proxy and firewall policy. Ask the host whether outbound TLS is filtered or intercepted and whether the remote API is rejecting the source address. The error does not establish that the plugin generated malformed data; it says the SSL connection could not be completed.
Nginx reports reset while reading upstream headers
Follow the FastCGI path: socket or address, PHP-FPM process health, pool limits, PHP fatal logs and timeouts. If the upstream is another proxy, inspect that proxy’s TLS and health logs instead. Do not “fix” this message by increasing every timeout before checking for a crashing or killed PHP worker.
Only an administrator screen, upload, comment or integration fails
Capture the exact request path and isolate plugins, the theme and the external service. A corrupted plugin is one documented possibility; a remote API, WAF rule or expired integration credential can produce the same narrow symptom. Reinstall or remove the identified plugin only after a one-at-a-time test ties it to the reset.
Visitors and administrators cannot connect to many routes
Check the client-to-origin path: DNS, certificate, reverse proxy, firewall and protocol negotiation. Test from more than one network and, where permitted, test the origin without the proxy. Preserve the proxy and origin logs together so the host can see which side sent the reset.
When to involve your host or server administrator
Escalate when you lack access to Nginx, PHP-FPM, TLS or firewall configuration, when workers are repeatedly dying, or when the reset persists after a clean plugin isolation. Send a compact incident bundle:
- UTC timestamp and timezone, frequency and affected routes;
- full browser, cURL or Nginx error line;
- client and server IP addresses, hostname and request path;
- Nginx or Apache, PHP and PHP-FPM excerpts surrounding the event;
- cURL verbose output with secrets, authorization headers and cookies removed;
- WAF, firewall, reverse-proxy and external-service request IDs where available;
- recent deployments, PHP or certificate changes, plugin updates and configuration reloads.
Ask the provider to identify which process issued the TCP reset, whether a proxy terminated TLS, and whether resource or security limits were reached. Those questions are more actionable than asking them simply to “restart WordPress.”
Preventing repeat resets
- Keep PHP, cURL/OpenSSL, WordPress, plugins and themes on supported versions, testing updates before production.
- Monitor Nginx, PHP-FPM and outbound-request failures with timestamps so intermittent resets can be correlated.
- Document every proxy and TLS termination point, including the hostname used for SNI and the upstream address.
- Set resource and timeout limits deliberately, based on observed request behavior rather than copying values between servers.
- Keep a maintenance procedure for one-at-a-time plugin isolation and a tested backup before reinstalling or removing components.
- Give managed hosting support the complete evidence bundle; they can inspect layers that a WordPress administrator cannot.
There is no universal WordPress toggle that cures this error. The reliable fix is the one that matches the hop that reset: repair the outbound TLS stack or network path for cURL 35, restore a healthy PHP-FPM/upstream boundary for Nginx 104, correct proxy SSL forwarding when that is the cause, or isolate and replace the plugin or integration that triggers the failing request.
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