CVE-2024-56140 is a medium-severity (CVSS 5.9) Cross-Site Request Forgery (CSRF) vulnerability in astro. A fix is available for astro — see the affected versions and patch details below.
Bypass of CSRF Middleware in Astro
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-56140.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2024-56140 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
astronpmDescription
Summary
A bug in Astro’s CSRF-protection middleware allows requests to bypass CSRF checks.
Details
When the security.checkOrigin configuration option is set to true, Astro middleware will perform a CSRF check. (Source code: https://github.com/withastro/astro/blob/6031962ab5f56457de986eb82bd24807e926ba1b/packages/astro/src/core/app/middlewares.ts)
For example, with the following Astro configuration:
// astro.config.mjs
import { defineConfig } from 'astro/config';
import node from '@astrojs/node';
export default defineConfig({
output: 'server',
security: { checkOrigin: true },
adapter: node({ mode: 'standalone' }),
});
A request like the following would be blocked if made from a different origin:
// fetch API or <form action="https://test.example.com/" method="POST">
fetch('https://test.example.com/', {
method: 'POST',
credentials: 'include',
body: 'a=b',
headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
});
// => Cross-site POST form submissions are forbidden
However, a vulnerability exists that can bypass this security.
Pattern 1: Requests with a semicolon after the Content-Type
A semicolon-delimited parameter is allowed after the type in Content-Type.
Web browsers will treat a Content-Type such as application/x-www-form-urlencoded; abc as a simple request and will not perform preflight validation. In this case, CSRF is not blocked as expected.
fetch('https://test.example.com', {
method: 'POST',
credentials: 'include',
body: 'test',
headers: { 'Content-Type': 'application/x-www-form-urlencoded; abc' },
});
// => Server-side functions are executed (Response Code 200).
Pattern 2: Request without Content-Type header
The Content-Type header is not required for a request. The following examples are sent without a Content-Type header, resulting in CSRF.
// Pattern 2.1 Request without body
fetch('http://test.example.com', { method: 'POST', credentials: 'include' });
// Pattern 2.2 Blob object without type
fetch('https://test.example.com', {
method: 'POST',
credentials: 'include',
body: new Blob(['a=b'], {}),
});
Impact
Bypass CSRF protection implemented with CSRF middleware.
[!Note] Even with
credentials: 'include', browsers may not send cookies due to third-party cookie blocking. This feature depends on the browser version and settings, and is for privacy protection, not as a CSRF measure.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | astro | all versions | 4.16.17npm install astro@4.16.17 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for astro, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update astro to 4.16.17 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-56140 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2024-56140 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2024-56140. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2024-56140 in your dependencies?
O3 Security finds CVE-2024-56140 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.