nginx protocol_error ai_generated true

upstream sent invalid Connection header while reading response header from upstream

ID: nginx/upstream-sent-invalid-connection-header

Also available as: JSON · Markdown

90%Fix Rate

85%Confidence

1Evidence

2024-06-22First Seen

Version Compatibility

Version	Status	Introduced	Deprecated	Notes
nginx 1.24.0	active	—	—	—
nginx 1.25.3	active	—	—	—
nginx 1.26.0	active	—	—	—

Root Cause

Upstream server returns a malformed or non-compliant 'Connection' header (e.g., multiple values, invalid token) that nginx rejects.

generic

Official Documentation

https://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_ignore_headers

Workarounds

90% success Use proxy_ignore_headers to ignore the Connection header from upstream: location / { proxy_pass http://upstream; proxy_ignore_headers Connection; }
```
Use proxy_ignore_headers to ignore the Connection header from upstream:
  location / {
      proxy_pass http://upstream;
      proxy_ignore_headers Connection;
  }
```
95% success Fix the upstream application to emit a valid Connection header (e.g., 'close' or 'keep-alive' only, no duplicates). For example, in a Node.js app: res.setHeader('Connection', 'keep-alive'); // Remove any duplicate or malformed Connection headers
```
Fix the upstream application to emit a valid Connection header (e.g., 'close' or 'keep-alive' only, no duplicates). For example, in a Node.js app:
  res.setHeader('Connection', 'keep-alive');
  // Remove any duplicate or malformed Connection headers
```

中文步骤

Use proxy_ignore_headers to ignore the Connection header from upstream:
  location / {
      proxy_pass http://upstream;
      proxy_ignore_headers Connection;
  }

Fix the upstream application to emit a valid Connection header (e.g., 'close' or 'keep-alive' only, no duplicates). For example, in a Node.js app:
  res.setHeader('Connection', 'keep-alive');
  // Remove any duplicate or malformed Connection headers

Dead Ends

Common approaches that don't work:

Add proxy_set_header Connection ''; 80% fail
This only affects request headers sent to upstream, not response headers from upstream.
Clear nginx cache 100% fail
Caching does not cause or fix header validation issues.
Upgrade nginx to latest version 60% fail
The issue is usually in the upstream application, not nginx itself.