CVE-2026-27118 Cache poisoning in @sveltejs/adapter-vercel
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-27118?
CVE-2026-27118 is a medium-severity vulnerability in sveltejs kit, published on 20 Feb 2026.
Official description
SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. Versions of @sveltejs/adapter-vercel prior to 6.3.2 are vulnerable to cache poisoning. An internal query parameter intended for Incremental Static Regeneration (ISR) is accessible on all routes, allowing an attacker to cause sensitive user-specific responses to be cached and served to other users. Successful exploitation requires a victim to visit an attacker-controlled link while authenticated. Existing deployments are protected by Vercel's WAF, but users should upgrade as soon as possible. This vulnerability is fixed in 6.3.2.
Weakness: CWE-346
Which versions are affected by CVE-2026-27118?
2 open source packages ship an affected version, including @sveltejs/adapter-vercel.
| Package | Affected | Fixed in |
|---|---|---|
@sveltejs/adapter-vercel npm | All versions | 6.3.2 |
@sveltejs/adapter-vercel npm | All versions | 6.3.2 |
How do I fix CVE-2026-27118?
Upgrade @sveltejs/adapter-vercel to 6.3.2 or later.
Is CVE-2026-27118 being exploited?
There is no known exploitation of CVE-2026-27118 in the wild and no public exploit code.
Sources
Also known as GHSA-9pq4-5hcf-288c.