CVE-2025-49005: vercel Request Smuggling

Description

Next.js is a React framework for building full-stack web applications. In Next.js App Router from 15.3.0 to before 15.3.3 and Vercel CLI from 41.4.1 to 42.2.0, a cache poisoning vulnerability was found. The issue allowed page requests for HTML content to return a React Server Component (RSC) payload instead under certain conditions. When deployed to Vercel, this would only impact the browser cache, and would not lead to the CDN being poisoned. When self-hosted and deployed externally, this could lead to cache poisoning if the CDN does not properly distinguish between RSC / HTML in the cache keys. This issue has been resolved in Next.js 15.3.3.

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CVSS v3.1 Score

3.7

LOW

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Weakness Type (CWE)

CWE-444 CWE-444

Affected Products

Vendor	Product	Versions
vercel	next.js	15.3.0 — 15.3.3
vercel	vercel	41.4.1 — 42.2.0

References

Advisories & Patches

https://github.com/vercel/next.js/commit/ec202eccf05820b60c6126d6411fe16766ecc066 https://github.com/vercel/next.js/security/advisories/GHSA-r2fc-ccr8-96c4 https://vercel.com/changelog/cve-2025-49005

Exploits

https://github.com/vercel/next.js/issues/79346 https://github.com/vercel/next.js/issues/79346

Other References

https://github.com/vercel/next.js/releases/tag/v15.3.3

Frequently Asked Questions

What is CVE-2025-49005? +

Next.js is a React framework for building full-stack web applications. In Next.js App Router from 15.3.0 to before 15.3.3 and Vercel CLI from 41.4.1 to 42.2.0, a cache poisoning vulnerability was found. The issue allowed page requests for HTML content to return a React Server Component (RSC) payload instead under certain conditions. When deployed to Vercel, this would only impact the browser cache, and would not lead to the CDN being poisoned. When self-hosted and deployed externally, this could lead to cache poisoning if the CDN does not properly distinguish between RSC / HTML in the cache keys. This issue has been resolved in Next.js 15.3.3. It has a CVSS v3.1 base score of 3.7 (LOW).

How severe is CVE-2025-49005? +

CVE-2025-49005 has a CVSS v3.1 score of 3.7 out of 10, rated LOW. This is a low-severity vulnerability with limited impact.

What products are affected by CVE-2025-49005? +

CVE-2025-49005 affects products from vercel, specifically: next.js, vercel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-49005? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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