GHSA-4233-jc72-56c5

## Summary

The `@astrojs/netlify` adapter generated regular expressions for Netlify Image CDN remote-image allowlists without anchoring them to the beginning of the URL. Netlify evaluates these expressions with `RegExp.test()`, so an allowed image origin appearing anywhere in a URL, including its path or query string, could satisfy the allowlist.

For example, an application allowing `images.example.com` could accept a source URL such as:

```text http://127.0.0.1:6379/?url=https://images.example.com/image.png ```

The allowlist matched the approved origin in the query string, but Netlify parsed and fetched the URL whose actual host was `127.0.0.1`.

## Impact

An unauthenticated attacker can bypass the configured `image.domains` or `image.remotePatterns` allowlist through the public `/.netlify/images` endpoint and cause Netlify Image CDN to make requests to attacker-selected URLs. This may allow probing or reaching internal services, depending on Netlify's network-level egress protections.

The Image CDN attempts to transform responses as images, which limits direct response exfiltration. No confidentiality or integrity impact has been demonstrated.

## Affected versions

`@astrojs/netlify` versions from 5.2.0 through 8.2.3.

## Patches

Fixed in `@astrojs/netlify` 8.2.4. Generated remote-image allowlist expressions are now anchored to both the beginning and end of the source URL.

## Workarounds

Upgrade to `@astrojs/netlify` 8.2.4 or later. Before upgrading, disable Netlify Image CDN by setting `imageCDN: false` in the adapter configuration, or remove remote image allowlist entries.

## Credits

Reported by @pacocartones.