CVE-2021-37699Network attack vector

Open redirect via encoded static error-page paths

Published Aug 11, 2021 · Updated Aug 4, 2024

Open redirect in Next.js 10.0.5 through 10.2.0 and 11.0.0 through 11.0.1 allows remote attackers to redirect users via encoded paths. The statically generated pages/_error.js route improperly parses specially encoded request paths beginning with a double slash and domain as an external redirect target. Exposure requires an affected error-page configuration; Vercel deployments and applications with pages/404.js are unaffected, and phishing requires a user to follow the crafted link.

CVSS severity6.9
Medium
EPSS probability1.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Open redirect in Next.js 10.0.5 through 10.2.0 and 11.0.0 through 11.0.1 allows remote attackers to redirect users via encoded paths. The statically generated pages/_error.js route improperly parses specially encoded request paths beginning with a double slash and domain as an external redirect target. Exposure requires an affected error-page configuration; Vercel deployments and applications with pages/404.js are unaffected, and phishing requires a user to follow the crafted link.

The record

CVE
CVE-2021-37699
Published
Aug 11, 2021
Updated
Aug 4, 2024
Vendor
Vercel
Product
Next.js
Classifications
CWE-601, T1566.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 11, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 11.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Vercel · Next.jsversion=< 11.1.0

Published CVSS scores

6.9GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-601URL Redirection to Untrusted Site ('Open Redirect')
T1566.002Spearphishing Link

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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