Answer in brief
CVE-2026-29057 records a Unknown severity vulnerability in Next.js: HTTP request smuggling in rewrites. The current sources do not mark it as known exploited. The current feed maps next (npm), next (npm). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps next (npm), next (npm). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| nextnpm | >=16.0.0-beta.0 <16.1.7 | 16.1.7 |
| nextnpm | >=9.5.0 <15.5.13 | 15.5.13 |
Published upstream
Mar 17, 2026
Evidence: source:osv:source_dates:source-dates:recordSource modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:recordFirst seen by HOL
Sep 10, 2026
## Summary 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. ## Impact 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. ## Patches The vulnerability originated in an upstream library vendored by Next.js. It is fixed 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. ## Workarounds If upgrade is not immediately possible: - Block chunked `DELETE`/`OPTIONS` requests on rewritten routes at your edge/proxy. - Enforce authentication/authorization on backend routes per our [security guidance](https://nextjs.org/docs/app/guides/data-security).
Quoted source text, attributed separately from HOL analysis.