CVE-2021-43812Network attack vector

Open redirect via incomplete returnTo validation

Published Dec 16, 2021 · Updated Aug 4, 2024

Open redirect in Auth0 Next.js SDK before 1.6.2 allows remote attackers to redirect users off-site through a crafted returnTo value. The login handler accepted returnTo values after regex checks for double slashes and URI schemes instead of validating the resolved URL's origin. Exploitation requires a user to follow the crafted login URL and complete authentication, after which the application redirects the user off-site.

CVSS severity6.1
Medium
EPSS probability0.66%
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 Auth0 Next.js SDK before 1.6.2 allows remote attackers to redirect users off-site through a crafted returnTo value. The login handler accepted returnTo values after regex checks for double slashes and URI schemes instead of validating the resolved URL's origin. Exploitation requires a user to follow the crafted login URL and complete authentication, after which the application redirects the user off-site.

The record

CVE
CVE-2021-43812
Published
Dec 16, 2021
Updated
Aug 4, 2024
Vendor
Auth0
Product
Auth0 Next.js SDK
Classifications
CWE-601
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 16, 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=< 1.6.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Auth0 · Auth0 Next.js SDKversion=< 1.6.2

Published CVSS scores

5.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
6.4GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/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.

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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')

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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