# CVE-2026-29057: Next.js: HTTP request smuggling in rewrites

> CVE-2026-29057: Next.js: HTTP request smuggling in rewrites. CVSS 6.5 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-29057
Last updated: 2026-06-17T10:29:31Z

- Published: 2026-03-18 00:30 UTC · Updated: 2026-06-17 10:29 UTC · Assigner: GitHub\_M
- CVSS: 6.5 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- EPSS: 0.45%, 39th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-444

## 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.

## Affected vendors and products

- vercel: next.js

## Tracked companies

- [Vercel](https://rewindex.com/company/vercel.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-29057)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-29057)
- [https://github.com/vercel/next.js/commit/dc98c04f376c6a1df76ec3e0a2d07edf4abdabd6](https://github.com/vercel/next.js/commit/dc98c04f376c6a1df76ec3e0a2d07edf4abdabd6)
- [https://github.com/vercel/next.js/releases/tag/v15.5.13](https://github.com/vercel/next.js/releases/tag/v15.5.13)
- [https://github.com/vercel/next.js/releases/tag/v16.1.7](https://github.com/vercel/next.js/releases/tag/v16.1.7)
- [https://github.com/vercel/next.js/security/advisories/GHSA-ggv3-7p47-pfv8](https://github.com/vercel/next.js/security/advisories/GHSA-ggv3-7p47-pfv8)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-29057 · Markdown: https://rewindex.com/cve/CVE-2026-29057.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-29057 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:15:15.780Z