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Vulnerabilities

Vulnerability · CVE-2026-29057

Next.js is a React framework for building full-stack web applications.

Published Mar 18, 2026 · catalog updated Jun 17, 2026 · Next.js is a React

Check if you run it

No confirmed exploitation is on record for CVE-2026-29057. EPSS is 0.55%. Act only if a listed version of Next.js is a React is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Next.js is a React).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.55%
Remediation
Advisory link
Affected products
cpe vercel/next.js

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 / request using 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 is added only when both and are absent, and is no longer removed in that code path. If upgrading is not immediately possible, block chunked / requests on rewritten routes at the edge/proxy, and/or enforce authentication/authorization on backend routes.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe vercel/next.jsversion unspecified

How to fix CVE-2026-29057

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-29057. EPSS is 0.55%. Act only if a listed version of Next.js is a React is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-444: HTTP Request Smuggling. EPSS 0.55%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 18, 2026 · NIST NVD

    Detected

    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 / request using could trigger request boundary disagreement between the proxy and backend. This could allow request smuggling through rewritten routes. An attacker could smuggle a second requ

  2. Jun 17, 2026 · NIST NVD

    Updated

    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 / request using could trigger request boundary disagreement between the proxy and backend. This could allow request smuggling through rewritten routes. An attacker could smuggle a second requ

Sources

  • CVE.orgVulnerability recordCVE-2026-29057

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-29057

    30-day exploitation probability 0.5%

    first.org
  • NIST NVDVulnerability recordCVE-2026-29057

    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 / request using could tri

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.