Medium severity · published Jul 27, 2026
CVE-2026-64647
Next.js: Response Body Cache Confusion with Invalid UTF-8 Request Bodies
5.4
CVSS
0.3%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 24% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NE
next.js · vercel
>= 13.0.0, < 15.5.21; >= 16.0.0, < 16.2.11 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-64647
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-64647
Patch
https://github.com/vercel/next.js/commit/025bf4a5f7b47fb7758c4ebf1c931a61c451c082
Issue Tracking
https://github.com/vercel/next.js/pull/96008
Product
https://github.com/vercel/next.js/releases/tag/v15.5.21
Product
https://github.com/vercel/next.js/releases/tag/v16.2.11
Vendor Advisory
https://github.com/vercel/next.js/security/advisories/GHSA-4633-3j49-mh5q
More from next.js
10.0
CVE-2025-55182
Meta React Server Components Remote Code Execution Vulnerability
9.1
CVE-2025-29927
Next.js is a React framework for building full-stack web applications
9.0
CVE-2026-75604
Next.js: Unauthenticated Remote Code Execution on windows-hosted servers
8.6
CVE-2026-44578
Next.js: Server-side request forgery in applications using WebSocket upgrades
8.2
CVE-2026-94482
Next.js: Denial of Service in App Router using Server Actions