CVE-2021-37421Network attack vector

Admin portal access via spoofed proxy header

Published Aug 30, 2021 · Updated Aug 4, 2024

Origin validation error in Zoho ManageEngine ADSelfService Plus 6103 and earlier allows remote attackers to reach an IP-restricted admin portal. The portal trusts the client-controlled X-Forwarded-For header as the request source and accepts a whitelisted address supplied there. The bypass removes the network-origin gate but does not itself grant an administrator account or establish access to further portal functions.

CVSS severity9.8
Critical
EPSS probability2.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Origin validation error in Zoho ManageEngine ADSelfService Plus 6103 and earlier allows remote attackers to reach an IP-restricted admin portal. The portal trusts the client-controlled X-Forwarded-For header as the request source and accepts a whitelisted address supplied there. The bypass removes the network-origin gate but does not itself grant an administrator account or establish access to further portal functions.

The record

CVE
CVE-2021-37421
Published
Aug 30, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-345, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 30, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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-345Insufficient Verification of Data Authenticity
T1190Exploit Public-Facing Application

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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