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Vulnerabilities

Vulnerability · CVE-2021-40539

Zoho ManageEngine ADSelfService Plus Authentication Bypass Vulnerability

Published Sep 7, 2021 · catalog updated Jun 16, 2026 · Zoho ManageEngine

Patch now

CVE-2021-40539 is in the CISA known-exploited catalog, due Nov 17, 2021. Confirm Zoho ManageEngine against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Severity
Critical9.8
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
98.96%
Remediation
Remediation guidance
Affected products
cpe zohocorp/manageengine adselfservice plus · vendor Zoho ManageEngine

Zoho ManageEngine ADSelfService Plus contains an authentication bypass vulnerability affecting the REST API URLs which allow for remote code execution. VulnCheck canary evidence. Initial-access exploit intelligence.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe zohocorp/manageengine adselfservice plus6.1
  • vendor Zoho ManageEngineversion unspecified

How to fix CVE-2021-40539

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2021-40539 is in the CISA known-exploited catalog, due Nov 17, 2021. Confirm Zoho ManageEngine against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Compare what you have installed with zohocorp/manageengine adselfservice plus 6.1. Apply updates per vendor instructions.

What should an analyst verify?

CWE-55; CWE-706. EPSS 98.96%. The CISA KEV listing is the exploitation evidence. A public exploit reference is linked in Sources. That is not the same as confirmed exploitation. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Sep 7, 2021 · Catalog

    Detected

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

  2. Nov 3, 2021 · CISA KEV

    Known exploited

    Apply updates per vendor instructions.

  3. Nov 17, 2021 · CISA KEV

    Remediation due

    Apply updates per vendor instructions.

  4. Jun 16, 2026 · Catalog

    Updated

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

Sources

  • CISA KEVConfirmed exploitationCVE-2021-40539

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

    cisa.gov
  • CVE.orgVulnerability recordCVE-2021-40539

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-40539

    30-day exploitation probability 99.0%

    first.org
  • Metasploit ModulesPublic exploit moduleexploit_windows/http/manageengine_adselfservice_plus_cve_2021_40539

    Public module reference (excellent). Module source is not copied into this catalog.

    rapid7.com
  • NIST NVDVulnerability recordCVE-2021-40539

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

    nvd.nist.gov
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/165085/ManageEngine-ADSelfService-Plus-Authentication-Bypass-Code-Execution.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com
  • VulnCheck KEVConfirmed exploitationCVE-2021-40539

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

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.