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CVE-2021-40539

9.8, critical Known exploited Used in ransomware

Zoho ManageEngine ADSelfService Plus Authentication Bypass Vulnerability

NVD (opens in a new tab) CVE.org (opens in a new tab) CISA KEV catalogue (opens in a new tab)
CVSS
9.8, critical critical CVSS v3.1
EPSS, next 30 days
99% higher than 99.9% of scored CVEs
Exploitation
Confirmed in the wild
Published
7 Sept 20215 years ago

Known exploited

CISA added this to the Known Exploited Vulnerabilities Catalog on 3 Nov 2021 and links it to ransomware activity. US federal agencies had to remediate by 17 Nov 2021, a deadline that has passed.

Required action. Apply updates per vendor instructions.

Description

Zoho ManageEngine ADSelfService Plus version 6113 and prior is vulnerable to REST API authentication bypass with resultant remote code execution.

Details

Vendor
Zoho
Product
Manageengine Adselfservice Plus
Weakness
CWE-706 (opens in a new tab)
Status
Analyzed
Updated
17 Jun 2026
Assigner
cve@mitre.org

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References 4

Exploit code 1

Patches and fixes 1

Other references 2

The kind is read from NVD's tags where present and from the shape of the URL otherwise, so treat it as a hint.

Other Zoho CVEs

Every Zoho CVE we hold

Same vendor in what we hold, not a known link between the flaws.

  • CVE-2022-47966 Zoho ManageEngine Multiple Products Remote Code Execution Vulnerability KEV EPSS 100% 9.8, critical
  • CVE-2022-35405 Zoho ManageEngine Multiple Products Remote Code Execution Vulnerability KEV EPSS 100% 9.8, critical
  • CVE-2022-28810 Zoho ManageEngine ADSelfService Plus Remote Code Execution Vulnerability KEV EPSS 71% 6.8, medium
  • CVE-2021-44515 Zoho Desktop Central Authentication Bypass Vulnerability KEV EPSS 100% 9.8, critical
  • CVE-2021-44077 Zoho ManageEngine ServiceDesk Plus Remote Code Execution Vulnerability KEV EPSS 93% 9.8, critical
  • CVE-2021-37415 Zoho ManageEngine ServiceDesk Authentication Bypass Vulnerability KEV EPSS 100% 9.8, critical
  • CVE-2020-10189 Zoho ManageEngine Desktop Central File Upload Vulnerability KEV EPSS 100% 9.8, critical
  • CVE-2019-8394 Zoho ManageEngine ServiceDesk Plus (SDP) File Upload Vulnerability KEV EPSS 63% 6.5, medium

Beyond this page

Is CVE-2021-40539 in your network?

This page tells you how dangerous CVE-2021-40539 is out there. Whether it sits on one of your devices, only a scan of your own network can tell. That is what our systems do, every day, for the companies we protect.

CVE-2021-40539 is in the CISA catalogue of exploited vulnerabilities: attackers are already exploiting it.

  • EXYS7600 OCELOT

    Find it before attackers do

    Ocelot scans your network on a schedule and reports every vulnerability it finds by its CVE identifier, with its CVSS score and how many of your hosts are affected. A finding like CVE-2021-40539 comes with the devices to patch.

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  • EXYS7950 KONDRA

    Detect it if it's exploited

    Until the patch is applied, Kondra monitors your network, events and endpoints in real time. It keeps an inventory of the software installed on every endpoint, and its anomaly detection rules flag what an attacker does once inside.

    Learn more about EXYS7950 KONDRA
Check your exposure

Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 16 Oct 2026, not the live upstream state.