CVE-2023-29008: Cross-Site Request Forgery (CSRF) (CWE-352)
value: The SvelteKit framework offers developers an option to create simple REST APIs. This is done by defining a `+server.js` file, containing endpoint handlers for different HTTP methods.

SvelteKit provides out-of-the-box cross-site request forgery (CSRF) protection to its users. The protection is implemented at `kit/src/runtime/server/respond.js`. While the implementation does a sufficient job of mitigating common CSRF attacks, the protection can be bypassed in versions prior to 1.15.2 by simply specifying an upper-cased `Content-Type` header value. The browser will not send uppercase characters, but this check does not block all expected CORS requests.

If abused, this issue will allow malicious requests to be submitted from third-party domains, which can allow execution of operations within the context of the victim's session, and in extreme scenarios can lead to unauthorized access to users’ accounts. This may lead to all POST operations requiring authentication being allowed in the following cases: If the target site sets `SameSite=None` on its auth cookie and the user visits a malicious site in a Chromium-based browser; if the target site doesn't set the `SameSite` attribute explicitly and the user visits a malicious site with Firefox/Safari with tracking protections turned off; and/or if the user is visiting a malicious site with a very outdated browser.

SvelteKit 1.15.2 contains a patch for this issue. It is also recommended to explicitly set `SameSite` to a value other than `None` on authentication cookies especially if the upgrade cannot be done in a timely manner.
CWE description: The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request.
CVSS v3 base score: 8.8
Published: 2023-04-06T17:15Z
Repository: https://github.com/sveltejs/kit
Language: JavaScript
Files changed: .changeset/happy-pots-move.md, packages/kit/src/utils/http.js, packages/kit/test/apps/basics/test/server.test.js
Commit date: 2023-04-06 08:45:55 -0700
Commit message: Merge pull request from GHSA-gv7g-x59x-wf8f

* fix: do a case-insensitive comparison when checking header value

* changeset

* remove export

* Update .changeset/happy-pots-move.md
Diff: diff --git a/.changeset/happy-pots-move.md b/.changeset/happy-pots-move.md
new file mode 100644
index 000000000..506c34b1c
--- /dev/null
+++ b/.changeset/happy-pots-move.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: address security advisory CVE-2023-29008 by doing a case-insensitive comparison when checking header value
diff --git a/packages/kit/src/utils/http.js b/packages/kit/src/utils/http.js
index f5bdf2ccf..739993449 100644
--- a/packages/kit/src/utils/http.js
+++ b/packages/kit/src/utils/http.js
@@ -57,13 +57,13 @@ export function negotiate(accept, types) {
 /**
  * Returns `true` if the request contains a `content-type` header with the given type
  * @param {Request} request
  * @param  {...string} types
  */
-export function is_content_type(request, ...types) {
+function is_content_type(request, ...types) {
 	const type = request.headers.get('content-type')?.split(';', 1)[0].trim() ?? '';
-	return types.includes(type);
+	return types.includes(type.toLowerCase());
 }
 
 /**
  * @param {Request} request
  */
diff --git a/packages/kit/test/apps/basics/test/server.test.js b/packages/kit/test/apps/basics/test/server.test.js
index ce31f520f..d6fc639ab 100644
--- a/packages/kit/test/apps/basics/test/server.test.js
+++ b/packages/kit/test/apps/basics/test/server.test.js
@@ -59,11 +59,12 @@ test.describe('Cookies', () => {
 test.describe('CSRF', () => {
 	test('Blocks requests with incorrect origin', async ({ baseURL }) => {
 		const content_types = [
 			'application/x-www-form-urlencoded',
 			'multipart/form-data',
-			'text/plain'
+			'text/plain',
+			'text/plaiN'
 		];
 		const methods = ['POST', 'PUT', 'PATCH', 'DELETE'];
 		for (const method of methods) {
 			for (const content_type of content_types) {
 				const res = await fetch(`${baseURL}/csrf`, {

Vulnerable code: export function is_content_type(request, ...types) {
	return types.includes(type);
			'text/plain'
Fixed code: ---
'@sveltejs/kit': patch
---

fix: address security advisory CVE-2023-29008 by doing a case-insensitive comparison when checking header value
function is_content_type(request, ...types) {
	return types.includes(type.toLowerCase());
			'text/plain',
			'text/plaiN'