nginx protocol_error ai_generated partial

upstream sent invalid status line while reading response header from upstream: "HTTP/1.1 200 OK\r\n" (extra characters)

ID: nginx/upstream-sent-invalid-status-line-while-reading-response-header

Also available as: JSON · Markdown

85%Fix Rate

82%Confidence

1Evidence

2025-08-20First 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 sends a response with malformed status line, such as extra spaces, invalid characters, or non-standard HTTP version.

generic

Official Documentation

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

Workarounds

30% success Use a custom nginx module or Lua to sanitize upstream response. Example with lua-nginx-module: location / { rewrite_by_lua_block { -- This is a placeholder; actual sanitization would require body_filter_by_lua } body_filter_by_lua ' -- If you can modify headers, but status line is not easily modifiable in Lua -- Better to fix upstream '; proxy_pass http://upstream; }
```
Use a custom nginx module or Lua to sanitize upstream response. Example with lua-nginx-module:
  location / {
      rewrite_by_lua_block {
          -- This is a placeholder; actual sanitization would require body_filter_by_lua
      }
      body_filter_by_lua '
          -- If you can modify headers, but status line is not easily modifiable in Lua
          -- Better to fix upstream
      ';
      proxy_pass http://upstream;
  }
```
95% success Fix the upstream application to emit a valid HTTP status line. For example, in a Python server: # Ensure the response line is exactly "HTTP/1.1 200 OK\r\n" response = b"HTTP/1.1 200 OK\r\nContent-Length: 5\r\n\r\nhello" # Avoid extra characters or spaces after the status line
```
Fix the upstream application to emit a valid HTTP status line. For example, in a Python server:
  # Ensure the response line is exactly "HTTP/1.1 200 OK\r\n"
  response = b"HTTP/1.1 200 OK\r\nContent-Length: 5\r\n\r\nhello"
  # Avoid extra characters or spaces after the status line
```

中文步骤

Use a custom nginx module or Lua to sanitize upstream response. Example with lua-nginx-module:
  location / {
      rewrite_by_lua_block {
          -- This is a placeholder; actual sanitization would require body_filter_by_lua
      }
      body_filter_by_lua '
          -- If you can modify headers, but status line is not easily modifiable in Lua
          -- Better to fix upstream
      ';
      proxy_pass http://upstream;
  }

Fix the upstream application to emit a valid HTTP status line. For example, in a Python server:
  # Ensure the response line is exactly "HTTP/1.1 200 OK\r\n"
  response = b"HTTP/1.1 200 OK\r\nContent-Length: 5\r\n\r\nhello"
  # Avoid extra characters or spaces after the status line

Dead Ends

Common approaches that don't work:

Add proxy_set_header Host $host; 100% fail
This sets request headers, not response validation.
Increase proxy_read_timeout 100% fail
Timeout does not fix malformed response line.
Restart nginx 100% fail
Restarting does not change upstream behavior.