CVE-2021-40539: Zoho ManageEngine ADSelfService Plus Authentication Bypass Vulnerability
Reference page built from the source records below, each shown as its source publishes it. Dataset version ref-799f4d7342a6, updated 2026-11-02T23:39:54.475Z.
CISA Known Exploited Vulnerabilities
- Name
- Zoho ManageEngine ADSelfService Plus Authentication Bypass Vulnerability
- Vendor
- Zoho
- Product
- ManageEngine
- Added to the catalog
- 2021-11-03
- Due date for US federal agencies
- 2021-11-17
- Weaknesses
- CWE-55
- Catalog version
- 2026.10.30
Zoho ManageEngine ADSelfService Plus contains an authentication bypass vulnerability affecting the REST API URLs which allow for remote code execution.
Required action (CISA)
Apply updates per vendor instructions.
Ransomware use: CISA marks this vulnerability as known to be used in ransomware campaigns. CISA does not say which group used it.
Links in CISA's notes
Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json
NVD analysis
- Status
- Analyzed
- Published
- 2021-09-07T17:15:07.367
- Last modified
- 2026-06-17T04:07:06.460
- Weaknesses
- CWE-706
Zoho ManageEngine ADSelfService Plus version 6113 and prior is vulnerable to REST API authentication bypass with resultant remote code execution.
| Metric | Score | Severity | Vector | Scored by |
|---|---|---|---|---|
| CVSS 3.1 | 9.8 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H | [email protected] (Primary) |
| CVSS 3.1 | 9.8 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H | 134c704f-9b21-4f2e-91b3-4a467353bcc0 (Secondary) |
| CVSS 2.0 | 7.5 | HIGH | AV:N/AC:L/Au:N/C:P/I:P/A:P | [email protected] (Primary) |
References
- http://packetstormsecurity.com/files/165085/ManageEngine-ADSelfService-Plus-Authentication-Bypass-Code-Execution.html (Exploit, Third Party Advisory, VDB Entry)
- https://www.manageengine.com (Product)
- https://www.manageengine.com/products/self-service-password/kb/how-to-fix-authentication-bypass-vulnerability-in-REST-API.html (Patch, Vendor Advisory)
- http://packetstormsecurity.com/files/165085/ManageEngine-ADSelfService-Plus-Authentication-Bypass-Code-Execution.html (Exploit, Third Party Advisory, VDB Entry)
- https://www.manageengine.com (Product)
- https://www.manageengine.com/products/self-service-password/kb/how-to-fix-authentication-bypass-vulnerability-in-REST-API.html (Patch, Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40539 (US Government Resource)
This product uses the NVD API but is not endorsed or certified by the NVD.
Read on 2026-11-02T23:41:59.479Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2021-40539
CVE record
- Assigner
- mitre
- State
- PUBLISHED
- Published
- 2021-09-07T16:06:58.000Z
- Updated
- 2025-10-21T23:25:35.374Z
- Problem types
- n/a
Zoho ManageEngine ADSelfService Plus version 6113 and prior is vulnerable to REST API authentication bypass with resultant remote code execution.
References
- https://www.manageengine.com
- https://www.manageengine.com/products/self-service-password/kb/how-to-fix-authentication-bypass-vulnerability-in-REST-API.html
- http://packetstormsecurity.com/files/165085/ManageEngine-ADSelfService-Plus-Authentication-Bypass-Code-Execution.html
Read on 2026-11-03T01:08:56.881Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2021/40xxx/CVE-2021-40539.json
Detection rules (SigmaHQ)
SigmaHQ rules whose own tags name this CVE. Each rule page shows the rule as its author published it.
- ADSelfService Exploitation (status test, level high)
- CVE-2021-40539 Zoho ManageEngine ADSelfService Plus Exploit (status test, level critical)
Defensive techniques (MITRE D3FEND)
D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.
CWE-706: Use of Incorrectly-Resolved Name or Reference
- Model: Asset Vulnerability Enumeration (acts on Software)
- Harden: Credential Scrubbing (acts on Subroutine)
- Harden: Software Update (acts on Software)
- Model: Software Inventory (acts on Software)
- Harden: Domain Logic Validation (acts on Subroutine)
- Restore: Restore Software (acts on Software)
- Isolate: Application-based Process Isolation (acts on Subroutine)
- Harden: Variable Initialization (acts on Subroutine)
- Harden: Trusted Library (acts on Subroutine)
D3FEND ontology version 1.6.0.
Read on 2026-11-03T00:02:40.476Z under licence d3fend-terms-of-use@f98cbc7e from https://d3fend.mitre.org/api/weakness/cwe/CWE-706.json
MITRE D3FEND™ knowledge graph. © 2025 The MITRE Corporation.
"The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use D3FEND for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." Terms: https://d3fend.mitre.org/tou/
Sources and licences
CISA
Source: CISA Catalog of Known Exploited Vulnerabilities, version 2026.10.30, CC0 1.0. Use of this data does not imply endorsement by CISA or DHS.
National Vulnerability Database (NIST)
This product uses the NVD API but is not endorsed or certified by the NVD.
NVD API Terms of Use (NIST publications in the public domain, 17 U.S.C. 105)
CVE Program, The MITRE Corporation
Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation. CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy.
SigmaHQ
"ADSelfService Exploitation" by Tobias Michalski (Nextron Systems), Max Altgelt (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-emerging-threats/2021/Exploits/CVE-2021-40539/web_cve_2021_40539_adselfservice.yml.
Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-LicenseSigmaHQ
"CVE-2021-40539 Zoho ManageEngine ADSelfService Plus Exploit" by Sittikorn S, Nuttakorn Tungpoonsup (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-emerging-threats/2021/Exploits/CVE-2021-40539/web_cve_2021_40539_manageengine_adselfservice_exploit.yml.
Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-LicenseMITRE D3FEND
MITRE D3FEND™ knowledge graph. © 2025 The MITRE Corporation.
"The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use D3FEND for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." Terms: https://d3fend.mitre.org/tou/MITRE D3FEND Terms of Use (site + knowledge graph); source repo MIT
Cite this page
Dragons Eye Ransomware Tracker, "CVE-2021-40539: Zoho ManageEngine ADSelfService Plus Authentication Bypass Vulnerability",
entity page, dataset version ref-799f4d7342a6, updated 2026-11-02T23:39:54.475Z,
https://ransomware-tracker.com/cve/CVE-2021-40539 (accessed 2026-11-03).
Underlying source: CISA Catalog of Known Exploited Vulnerabilities, version 2026.10.30.
Underlying source: National Vulnerability Database (NIST), CVE API 2.0, record last modified 2026-06-17T04:07:06.460.
Underlying source: CVE List (CVE Program, The MITRE Corporation), record updated 2025-10-21T23:25:35.374Z.
Underlying source: SigmaHQ rule 6702b13c-e421-44cc-ab33-42cc25570f11, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.
Underlying source: SigmaHQ rule fcbb4a77-f368-4945-b046-4499a1da69d1, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.
Underlying source: MITRE D3FEND, ontology version 1.6.0.
Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.