CVE-2025-49826: next.js Request Smuggling — Fix

Description

Next.js is a React framework for building full-stack web applications. From versions 15.0.4-canary.51 to before 15.1.8, a cache poisoning bug leading to a Denial of Service (DoS) condition was found in Next.js. This issue does not impact customers hosted on Vercel. Under certain conditions, this issue may allow a HTTP 204 response to be cached for static pages, leading to the 204 response being served to all users attempting to access the page. This issue has been addressed in version 15.1.8.

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CVSS v3.1 Score

7.5

HIGH

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

Weakness Type (CWE)

CWE-444 CWE-444

Affected Products

Vendor	Product	Versions
vercel	next.js	< 15.1.8
vercel	next.js	All
vercel	next.js	All

References

Advisories & Patches

https://github.com/vercel/next.js/commit/a15b974ed707d63ad4da5b74c1441f5b7b120e93 https://github.com/vercel/next.js/security/advisories/GHSA-67rr-84xm-4c7r https://vercel.com/changelog/cve-2025-49826

Other References

https://github.com/vercel/next.js/releases/tag/v15.1.8

Frequently Asked Questions

What is CVE-2025-49826? +

Next.js is a React framework for building full-stack web applications. From versions 15.0.4-canary.51 to before 15.1.8, a cache poisoning bug leading to a Denial of Service (DoS) condition was found in Next.js. This issue does not impact customers hosted on Vercel. Under certain conditions, this issue may allow a HTTP 204 response to be cached for static pages, leading to the 204 response being served to all users attempting to access the page. This issue has been addressed in version 15.1.8. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2025-49826? +

CVE-2025-49826 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-49826? +

CVE-2025-49826 affects products from vercel, specifically: next.js. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-49826? +

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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