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Moderate severityNVD Advisory· Published Aug 8, 2025· Updated Aug 8, 2025

Astro: Duplicate trailing slash feature can lead to Open Redirects

CVE-2025-54793

Description

Astro is a web framework for content-driven websites. In versions 5.2.0 through 5.12.7, there is an Open Redirect vulnerability in the trailing slash redirection logic when handling paths with double slashes. This allows an attacker to redirect users to arbitrary external domains by crafting URLs such as https://mydomain.com//malicious-site.com/. This increases the risk of phishing and other social engineering attacks. This affects sites that use on-demand rendering (SSR) with the Node or Cloudflare adapters. It does not affect static sites, or sites deployed to Netlify or Vercel. This issue is fixed in version 5.12.8. To work around this issue at the network level, block outgoing redirect responses with a Location header value that starts with //.

Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
astronpm
>= 5.2.0, < 5.12.85.12.8

Affected products

1

Patches

1
0567fb7b50c0

Merge commit from fork

https://github.com/withastro/astroMatt KaneAug 1, 2025via ghsa
commit
3 files changed · +10 −1
  • .changeset/easy-turtles-kiss.md+6 −0 added
    @@ -0,0 +1,6 @@
+---
+'@astrojs/internal-helpers': patch
+'astro': patch
+---
+
+Adds `//` to list of internal path prefixes that do not have automated trailing slash handling
  • packages/astro/test/ssr-trailing-slash.test.js+3 −0 modified
    @@ -116,6 +116,7 @@ describe('Redirecting trailing slashes in SSR', () => {
 				'/_server-islands/foo',
 				'/_actions/foo',
 				'/.netlify/image?url=http://example.com/foo.jpg',
+				'//target.example/path',
 			]) {
 				const request = new Request(`http://example.com${path}`);
 				const response = await app.render(request);
@@ -213,6 +214,7 @@ describe('Redirecting trailing slashes in SSR', () => {
 				'/_server-islands/foo/',
 				'/_actions/foo/',
 				'/.netlify/image/?url=http://example.com/foo.jpg',
+				'//target.example/path/',
 			]) {
 				const request = new Request(`http://example.com${path}/`);
 				const response = await app.render(request);
@@ -271,6 +273,7 @@ describe('Redirecting trailing slashes in SSR', () => {
 				'/_server-islands/foo//',
 				'/_actions/foo//',
 				'/.netlify/image//?url=http://example.com/foo.jpg',
+				'//target.example/path//',
 			]) {
 				const request = new Request(`http://example.com${path}/`);
 				const response = await app.render(request);
  • packages/internal-helpers/src/path.ts+1 −1 modified
    @@ -69,7 +69,7 @@ function isString(path: unknown): path is string {
 	return typeof path === 'string' || path instanceof String;
 }
 
-const INTERNAL_PREFIXES = new Set(['/_', '/@', '/.']);
+const INTERNAL_PREFIXES = new Set(['/_', '/@', '/.', '//']);
 const JUST_SLASHES = /^\/{2,}$/;
 
 export function isInternalPath(path: string) {

Vulnerability mechanics

Generated by null/stub on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

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News mentions

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