CVE-2026-29057

MEDIUM EPSS 34.3%
Published Mar 18, 20263mo ago · Modified Jun 17, 20261w ago
6.3 CVSS 4.0
Medium
Find Similar
Published Mar 18, 2026 3mo ago
Last Modified Jun 17, 2026 1w ago

Description

Next.js is a React framework for building full-stack web applications. Starting in version 9.5.0 and prior to versions 15.5.13 and 16.1.7, when Next.js rewrites proxy traffic to an external backend, a crafted `DELETE`/`OPTIONS` request using `Transfer-Encoding: chunked` could trigger request boundary disagreement between the proxy and backend. This could allow request smuggling through rewritten routes. An attacker could smuggle a second request to unintended backend routes (for example, internal/admin endpoints), bypassing assumptions that only the configured rewrite destination/path is reachable. This does not impact applications hosted on providers that handle rewrites at the CDN level, such as Vercel. The vulnerability originated in an upstream library vendored by Next.js. It is fixed in Next.js 15.5.13 and 16.1.7 by updating that dependency’s behavior so `content-length: 0` is added only when both `content-length` and `transfer-encoding` are absent, and `transfer-encoding` is no longer removed in that code path. If upgrading is not immediately possible, block chunked `DELETE`/`OPTIONS` requests on rewritten routes at the edge/proxy, and/or enforce authentication/authorization on backend routes.

CVSS Details

Base Score
6.3
Exploitability
—
Impact
—
Vector string
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: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
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope X

Threat Intelligence

EPSS Exploit Probability
34.3% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Weaknesses 1

CWE-444

Affected Products 2

VendorProductVersionRange
vercelnext.js*≥9.5.0  –  <15.5.13
vercelnext.js*≥16.0.0  –  <16.1.7

References 4

  • github.com https://github.com/vercel/next.js/commit/dc98c04f376c6a1df76ec3e0a2d07edf4abdabd6
    Patch
  • github.com https://github.com/vercel/next.js/releases/tag/v15.5.13
    ProductRelease Notes
  • github.com https://github.com/vercel/next.js/releases/tag/v16.1.7
    ProductRelease Notes
  • github.com https://github.com/vercel/next.js/security/advisories/GHSA-ggv3-7p47-pfv8
    MitigationVendor Advisory

Remediation

  • github.com https://github.com/vercel/next.js/commit/dc98c04f376c6a1df76ec3e0a2d07edf4abdabd6
    Patch