CVE-2023-29008 is a high-severity (CVSS 8.8) Server-Side Request Forgery (SSRF) vulnerability in @sveltejs/kit. A fix is available for @sveltejs/kit — see the affected versions and patch details below.
SvelteKit framework has Insufficient CSRF protection for CORS requests
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.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-29008.
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-2023-29008 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 377,238 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.
@sveltejs/kitnpmDescription
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @sveltejs/kit | all versions | 1.15.2npm install @sveltejs/kit@1.15.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @sveltejs/kit, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @sveltejs/kit to 1.15.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-29008 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-2023-29008 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-29008. 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-2023-29008 in your dependencies?
O3 Security finds CVE-2023-29008 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.