CVE-2026-64647
Next.js: Cache confusion of response bodies for requests with bodies containing invalid UTF-8 byte sequences
Impact
Next.js is a React framework for building full-stack web applications. In versions 12.0.0 through 15.5.20 and 16.0.0 through 16.2.10, a server-side fetch with a request body may return a cached response body from a different request to the same URL but different body. Confidential data in the POST's response body would then leak to unauthorized requests. Though the request itself will not be deduped. This is only an issue when receiving request bodies with a content type charset other than UTF-8. For example, the UTF-16 byte sequences for 삃삃 and 섄섄 in the request body would share the same cache. This issue has been fixed in versions 15.5.21 and 16.2.11.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | next | >= 13.0.0, < 15.5.21 | 15.5.21 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Vercel | Next.Js | from 13.0.0 before 15.5.21 from 16.0.0 before 16.2.11 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-4633-3j49-mh5q
- https://github.com/vercel/next.js/security/advisories/GHSA-4633-3j49-mh5q
- https://github.com/vercel/next.js/pull/96008
- https://github.com/vercel/next.js/commit/025bf4a5f7b47fb7758c4ebf1c931a61c451c082
- https://github.com/vercel/next.js/releases/tag/v15.5.21
- https://github.com/vercel/next.js/releases/tag/v16.2.11