CVE-2021-40539

KEVRansomware UseZoho ManageEngine ADSelfService Plus Authentication Bypass Vulnerability

Description

Zoho ManageEngine ADSelfService Plus contains an authentication bypass vulnerability affecting the REST API URLs which allow for remote code execution.

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

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

PublishedSep 7, 2021

Last modifiedJun 17, 2026

Added to KEVNov 3, 2021

Remediation dueNov 17, 2021

References

packetstormsecurity.com/files/165085/ManageEngine-ADSelfService-Plus-Authentication-Bypass-Code-Execution.htmlExploitThird Party Advisory
manageengine.comProduct
manageengine.com/products/self-service-password/kb/how-to-fix-authentication-bypass-vulnerability-in-REST-API.htmlPatchVendor Advisory
cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40539US Government Resource

0 recent articles mention this CVE

Risk assessment · Critical

Actively exploited and used by ransomware crews. Patch immediately.

Exploitation: Confirmed in the wild (CISA KEV)
Federal remediation deadline: Overdue by 1804 days
Ransomware: Used in known ransomware campaigns
CVSS: 9.8 CRITICAL
EPSS (30-day exploit probability): 99.0% · top 1% of all CVEs
Weakness: CWE-706
Attack vector: Network, remotely reachable
Preconditions: No privileges and no user interaction

Recommended actions

1.Apply updates per vendor instructions.
2.Treat as emergency change: patch or isolate internet-facing instances first.
3.Review exposure: confirm which instances are reachable from the internet and restrict access until patched.
4.Hunt for compromise: review logs for the disclosure window, not just from the patch date.
5.Verify offline/immutable backups and segment the affected systems. This flaw is used for ransomware initial access.

Assessment is derived automatically from the live signals above; verify against your own asset inventory.