Question 1

How to mitigate NGINX CVE-2026-42945 rewrite directive heap buffer overflow?

Accepted Answer

Use named captures instead of unnamed captures (like $1, $2) in rewrite directives. For example, change `rewrite ^/users/([0-9]+)/profile/(.*)$ /profile.php?id=$1&tab=$2 last;` to `rewrite ^/users/(?[0-9]+)/profile/(?

.*)$ /profile.php?id=$user_id&tab=$section last;`. This prevents heap overflow when the rewrite is followed by rewrite, if, or set directives, and the replacement includes a `?`. For systems with ASLR disabled, this also mitigates potential code execution.

Question 2

How to fix 'Device or resource busy' error when mounting custom Nginx config in Nginx Proxy Manager?

Accepted Answer

This error occurs because Nginx Proxy Manager (NPM) attempts to modify files in `/etc/nginx/conf.d/include/` during startup, but Docker mount points cannot be moved or replaced. To resolve, use one of these methods: 1) Switch to the development Docker image `nginxproxymanager/nginx-proxy-manager-dev:develop`, which detects mounts and skips modification, logging 'WARNING: skipping ... — mounted file'; 2) Place custom configs in a different directory (e.g., `/etc/nginx/conf.d/custom/`) that you create and mount, then manually include them in a host that is not auto‑managed; 3) Use the NPM UI’s 'Custom locations' feature to inject custom Nginx directives without mounting files. Avoid mounting directly into `/etc/nginx/conf.d/include/`. A permanent fix will be included in a future stable release.

Question 3

How to stop nginx proxy manager logs from growing indefinitely and filling up disk space?

Accepted Answer

By default, nginx logs inside the container are not rotated, causing unlimited growth. Two solutions: (1) Set up logrotate on the Docker host with a config like:
/path/to/nginx/*.log {
    maxsize 500M
    daily
    rotate 14
    compress
    postrotate
        docker exec CONTAINER_NAME bash -c 'kill -USR1 `cat /var/run/nginx.pid`'
    endscript
}
(2) Redirect logs to stdout by customizing nginx.conf (e.g., adding 'error_log /dev/stdout warn; access_log /dev/stdout proxy;') and using Docker's logging driver (e.g., local or json-file) with max-size to control log size.

Question 4

How to fix 'no such function: NOW' SQLite error when creating a new user in Nginx Proxy Manager v2.13.7 on Docker?

Accepted Answer

This is a known bug in v2.13.7 where the SQLite NOW function was deprecated. As a temporary workaround, downgrade to version 2.13.6 (e.g., use image tag jc21/nginx-proxy-manager:2.13.6). Monitor the official releases for a permanent fix.

Question 5

Why does Nginx Proxy Manager custom location return 502 Bad Gateway after the backend Docker container is recreated?

Accepted Answer

The custom location's upstream IP is cached by nginx at config load time and isn't re-resolved when the backend container gets a new IP. Workaround: Re-save the affected proxy host in NPM UI (or restart the NPM container) to force nginx config regeneration. For a permanent fix, modify the custom location to use a resolver and variable: `resolver 127.0.0.11 valid=10s; set $upstream container_name:port; proxy_pass $upstream;`. Monitor issue #5602 for built-in dynamic resolver support.

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