What’s Vulnerable › Vulnerabilities

CVE-2025-49005: Next.js cache poisoning due to omission of Vary header

• Severity: low (CVSS 3.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2025-07-03 · updated 2026-06-17
• Weakness: CWE-444

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.

Affected products

• Next.js: from 15.3.0 before 15.3.3 — fixed in 15.3.3
• vercel: from 41.4.1 before 42.2.0 — fixed in 42.2.0

How to fix

Upgrade to a fixed version: Next.js 15.3.3; vercel 42.2.0. Check the vendor advisory for mitigations.

References

• https://github.com/vercel/next.js/commit/ec202eccf05820b60c6126d6411fe16766ecc066
• https://github.com/vercel/next.js/issues/79346
• https://github.com/vercel/next.js/releases/tag/v15.3.3
• https://github.com/vercel/next.js/security/advisories/GHSA-r2fc-ccr8-96c4
• https://vercel.com/changelog/cve-2025-49005
• https://github.com/vercel/next.js/issues/79346

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