Improper Encoding or Escaping of Output in Next.js - CVE-2026-64647
Published: July 22, 2026
Vulnerability identifier: #VU139034
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-64647
CWE-ID: CWE-116
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: vercel
Affected software:
Next.js
Next.js
Detailed vulnerability description
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to improper encoding or escaping of output in the server-side fetch response cache when processing requests with bodies containing invalid UTF-8 byte sequences. A remote attacker can send specially crafted requests to disclose sensitive information.
Only requests using a content type charset other than UTF-8 are affected, and the issue can cause a cached response body from one request to be returned for a different request to the same URL with a different body.
How to mitigate CVE-2026-64647
Install security update from vendor's website.