Astro is a web framework for content-driven websites. From 7.0.0 until 7.0.6, the composable astro/hono pipeline installs security.checkOrigin only through the middleware() primitive, while actions() and pages() can dispatch to user code independently. Mounting actions() before middleware(), as in the examples/advanced-routing example and Cloudflare Hono documentation, allows cross-origin form-encoded action requests to execute before the origin check, and using pages() without middleware() drops the check for on-demand endpoints and pages. The flaw enables blind write-only cross-site request forgery using the victim's cookies against ActionHandler.handle and PagesHandler.handleWithErrorFallback when manifest.checkOrigin is enabled; the attacker can trigger a state-mutating action or endpoint handler but cannot read the cross-origin response. The default non-composable astro() pipeline is not affected. This issue is fixed in version 7.0.6.
Astro is a web framework for content-driven websites. From 2.9.0 until 7.1.0, Astro's server-side View Transition CSS generator interpolates animation properties into an inline style element without escaping them for CSS and HTML contexts. An attacker-controlled View Transition animation value such as duration can terminate the generated style element and inject arbitrary HTML or JavaScript. The affected code is packages/astro/src/runtime/server/transition.ts; renderTransition passes sheet.toString() into markHTMLString(), while addAnimationProperty serializes duration through toTimeValue() and also handles easing, direction, delay, fillMode, and name. Exploitation requires an on-demand or server-rendered route to pass attacker-controlled data into a View Transition animation definition and can execute arbitrary JavaScript in the affected application's origin, allowing access to sensitive page data and authenticated actions available to the victim. This issue is fixed in version 7.1.0.
Astro is a web framework. Prior to 6.4.6, the spreadAttributes function in Astro's server-side rendering pipeline iterates over object keys and passes them directly to addAttribute, which interpolates the key into the HTML output without escaping. When a developer uses the spread syntax {...props} on an HTML element and the object keys come from an untrusted source (API, CMS, URL parameters), an attacker can inject arbitrary HTML attributes including event handlers like onmousemove, onclick, or break out of the attribute context entirely to inject new elements. This vulnerability is fixed in 6.4.6.
Astro is a web framework. Astro versions prior to 6.1.10 used AES-GCM encryption to protect the confidentiality and integrity of server island props and slots parameters, but did not bind the ciphertext to its intended component or parameter type. An attacker could replay one component's encrypted props (p) value as another component's slots (s) value, or vice versa. Since slots contain raw unescaped HTML while props may contain user-controlled values, this could lead to XSS in applications. This occurs when the application uses server islands, two different server island components share the same key name for a prop and a slot, and an attacker has full control over the value of the overlapping prop (requires a dynamically rendered page). This vulnerability is fixed in 6.1.10.
CVE-2026-41067 is a cross-site scripting (XSS) vulnerability in the Astro web framework versions prior to 6.1.6. The issue arises from improper sanitization in the defineScriptVars function, which uses a case-sensitive regex to sanitize inline <script> tag injections. Because HTML parsers treat script tag closures case-insensitively and accept variations with whitespace or slashes, attackers can bypass this sanitization and inject arbitrary HTML or JavaScript. This vulnerability has a CVSS score of 6.1 (medium severity) and is fixed in version 6.1.6.
CVE-2026-29772 is a medium-severity vulnerability in the Astro web framework versions prior to 10.0.0. The issue arises from the Server Islands POST handler, which parses the entire request body as JSON without enforcing any size limits. This allows an attacker to send a crafted payload containing many small JSON objects, causing approximately 15 times memory amplification in the V8 JavaScript engine heap. As a result, a single unauthenticated request can exhaust the server's memory and crash the process, leading to denial of service. The vulnerable endpoint is /_server-islands/[name], which is registered on all Astro SSR apps using the Node standalone adapter, regardless of component usage. The vulnerability has been patched in Astro version 10.0.0.
Astro is a web framework. In versions 9.0.0 through 9.5.3, Astro server actions have no default request body size limit, which can lead to memory exhaustion DoS. A single large POST to a valid action endpoint can crash the server process on memory-constrained deployments. On-demand rendered sites built with Astro can define server actions, which automatically parse incoming request bodies (JSON or FormData). The body is buffered entirely into memory with no size limit — a single oversized request is sufficient to exhaust the process heap and crash the server. Astro's Node adapter (`mode: 'standalone'`) creates an HTTP server with no body size protection. In containerized environments, the crashed process is automatically restarted, and repeated requests cause a persistent crash-restart loop. Action names are discoverable from HTML form attributes on any public page, so no authentication is required. The vulnerability allows unauthenticated denial of service against SSR standalone deployments using server actions. A single oversized request crashes the server process, and repeated requests cause a persistent crash-restart loop in containerized environments. Version 9.5.4 contains a fix.
Astro is a web framework. Versions 5.15.7 and below have a double URL encoding bypass which allows any unauthenticated attacker to bypass path-based authentication checks in Astro middleware, granting unauthorized access to protected routes. While the original CVE-2025-64765 was fixed in v5.15.8, the fix is insufficient as it only decodes once. By using double-encoded URLs, attackers can still bypass authentication and access any route protected by middleware pathname checks. This issue is fixed in version 5.15.8.
Astro is a web framework. Prior to version 5.15.8, a mismatch exists between how Astro normalizes request paths for routing/rendering and how the application’s middleware reads the path for validation checks. Astro internally applies decodeURI() to determine which route to render, while the middleware uses context.url.pathname without applying the same normalization (decodeURI). This discrepancy may allow attackers to reach protected routes using encoded path variants that pass routing but bypass validation checks. This issue has been patched in version 5.15.8.
Astro is a web framework. Prior to version 5.15.8, a reflected XSS vulnerability is present when the server islands feature is used in the targeted application, regardless of what was intended by the component template(s). This issue has been patched in version 5.15.8.
Astro is a web framework. Prior to version 5.15.9, when using Astro's Cloudflare adapter (@astrojs/cloudflare) with output: 'server', the image optimization endpoint (/_image) contains a critical vulnerability in the isRemoteAllowed() function that unconditionally allows data: protocol URLs. This enables Cross-Site Scripting (XSS) attacks through malicious SVG payloads, bypassing domain restrictions and Content Security Policy protections. This issue has been patched in version 5.15.9.
Astro is a web framework. Starting in version 5.2.0 and prior to version 5.15.6, a Reflected Cross-Site Scripting (XSS) vulnerability exists in Astro's development server error pages when the `trailingSlash` configuration option is used. An attacker can inject arbitrary JavaScript code that executes in the victim's browser context by crafting a malicious URL. While this vulnerability only affects the development server and not production builds, it could be exploited to compromise developer environments through social engineering or malicious links. Version 5.15.6 fixes the issue.