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Fencer Vulns
medium 5.4

CVE-2026-64647 json

Next.js: Response Body Cache Confusion with Invalid UTF-8 Request Bodies

published 2026-07-21 3 mo ago modified 2026-10-24 15 d ago also EUVD-2026-49404 , GHSA-4633-3j49-mh5q

cvss
5.4
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm next 15.5.21, 16.2.11
  • vercel next.js 15.5.21, 16.2.11

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-64647 updated cvss 3.7

next: Next.js: Information disclosure via server-side request caching

  • Red Hat Enterprise Linux 7 firefox, firefox 140.13.0-1.el10_2 Red Hat Enterprise Linux 8 firefox, thunderbird, firefox 140.13.0-1.el10_2, thunderbird 140.12.0-1.el10_0 Red Hat Enterprise Linux 9 firefox, firefox-x11, thunderbird, firefox 140.13.0-1.el10_2, thunderbird 140.12.0-1.el10_0 Red Hat Enterprise Linux 10 firefox 140.13.0-1.el10_2, thunderbird 140.12.0-1.el10_0 Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/disk-image-cuda-rhel9 Red Hat Trusted Artifact Signer rhtas/rekor-search-ui-rhel9
    affected: no fix available “Fix deferred”
  • Red Hat streams for Apache Kafka 2 next 15.5.18
    affected: no fix planned “Out of support scope”
  • Red Hat streams for Apache Kafka 3 next 15.5.18
    affected: no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
npm next
>=13.0.0, <15.5.21
>=16.0.0, <16.2.11
15.5.21
16.2.11

Affected products

  • vercel next.js

Classification

Weakness
  • CWE-116 Improper Encoding or Escaping of Output
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of vercel/next.js published their own advisory on GitHub. Reviewed sources take precedence over it.