Astro is a web framework. In Astro versions 2.16.0 up to but excluding 5.15.5 which utilizeon-demand rendering, request headers `x-forwarded-proto` and `x-forwarded-port` are insecurely used, without sanitization, to build the URL. This has several consequences, the most important of which are: middleware-based protected route bypass (only via `x-forwarded-proto`), DoS via cache poisoning (if a CDN is present), SSRF (only via `x-forwarded-proto`), URL pollution (potential SXSS, if a CDN is present), and WAF bypass. Version 5.15.5 contains a patch.

Astro is a web framework. Prior to version 5.14.2, Astro reflects the value in `X-Forwarded-Host` in output when using `Astro.url` without any validation. It is common for web servers such as nginx to route requests via the `Host` header, and forward on other request headers. As such as malicious request can be sent with both a `Host` header and an `X-Forwarded-Host` header where the values do not match and the `X-Forwarded-Host` header is malicious. Astro will then return the malicious value. This could result in any usages of the `Astro.url` value in code being manipulated by a request. For example if a user follows guidance and uses `Astro.url` for a canonical link the canonical link can be manipulated to another site. It is theoretically possible that the value could also be used as a login/registration or other form URL as well, resulting in potential redirecting of login credentials to a malicious party. As this is a per-request attack vector the surface area would only be to the malicious user until one considers that having a caching proxy is a common setup, in which case any page which is cached could persist the malicious value for subsequent users. Many other frameworks have an allowlist of domains to validate against, or do not have a case where the headers are reflected to avoid such issues. This could affect anyone using Astro in an on-demand/dynamic rendering mode behind a caching proxy. Version 5.14.2 contains a fix for the issue.

Astro is a web framework. Prior to version 9.5.4, Server-Side Rendered pages that return an error with a prerendered custom error page (eg. `404.astro` or `500.astro`) are vulnerable to SSRF. If the `Host:` header is changed to an attacker's server, it will be fetched on `/500.html` and they can redirect this to any internal URL to read the response body through the first request. An attacker who can access the application without `Host:` header validation (eg. through finding the origin IP behind a proxy, or just by default) can fetch their own server to redirect to any internal IP. With this they can fetch cloud metadata IPs and interact with services in the internal network or localhost. For this to be vulnerable, a common feature needs to be used, with direct access to the server (no proxies). Version 9.5.4 fixes the issue.

Astro is a web framework that includes an image proxy. In versions 5.13.4 and later before 5.13.10, the image proxy domain validation can be bypassed by using backslashes in the href parameter, allowing server-side requests to arbitrary URLs. This can lead to server-side request forgery (SSRF) and potentially cross-site scripting (XSS). This vulnerability exists due to an incomplete fix for CVE-2025-58179. Fixed in 5.13.10.

Astro is a web framework for content-driven websites. Versions 11.0.3 through 12.6.5 are vulnerable to SSRF when using Astro's Cloudflare adapter. When configured with output: 'server' while using the default imageService: 'compile', the generated image optimization endpoint doesn't check the URLs it receives, allowing content from unauthorized third-party domains to be served. a A bug in impacted versions of the @astrojs/cloudflare adapter for deployment on Cloudflare’s infrastructure, allows an attacker to bypass the third-party domain restrictions and serve any content from the vulnerable origin. This issue is fixed in version 12.6.6.