CVE-2021-40539
CRITICALCISA KEVEPSS 100th pctlDescription
Zoho ManageEngine ADSelfService Plus version 6113 and prior is vulnerable to REST API authentication bypass with resultant remote code execution.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploit Intelligence
Very high risk: more likely to be exploited than 100% of all known CVEs.
Zoho ManageEngine ADSelfService Plus Authentication Bypass Vulnerability
Zoho ManageEngine ADSelfService Plus contains an authentication bypass vulnerability affecting the REST API URLs which allow for remote code execution.
Apply updates per vendor instructions.
Remediation due: 2021-11-17
Associated with ransomware campaigns
References
Related Vulnerabilities
Other CWE-706 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-24813 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2020-15505 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2024-27292 | High | 7.5 | 69% | - | Fix |
| CVE-2021-40856 | High | 7.5 | 51% | - | - |
| CVE-2021-24122 | Medium | 5.9 | 23% | - | Fix |
| CVE-2019-0220 | Medium | 5.3 | 18% | - | Fix |
Common questions
How do I fix CVE-2021-40539?
Upgrade manageengine adselfservice plus to 6.1 or later.
Is CVE-2021-40539 being actively exploited?
Yes. CVE-2021-40539 is listed in the CISA Known Exploited Vulnerabilities catalog, which means exploitation has been observed in the wild. CISA has also linked it to known ransomware campaigns. US federal agencies were required to remediate it by 2021-11-17. Treat it as a priority whatever its CVSS score says.
How severe is CVE-2021-40539?
CVE-2021-40539 has a CVSS v3 base score of 9.8, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2021-40539 affect?
Published advisories record a fix for manageengine adselfservice plus (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
Embed a live status badge for CVE-2021-40539
Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-11-05.