Security Vulnerability CVE-2021-40539 - Complete Analysis and Details
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CVE-2021-40539

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This is a free service offered by Red Hot Cyber to the community. It allows you to view, on a single page, information about a single CVE from the National Vulnerability Database (NVD) and the National Institute of Standards and Technology (NIST) of the United States of America, the Forum of Incident Response and Security Teams (FIRST) regarding the EPSS score and percentile, data from the KEV catalog of the Cybersecurity and Infrastructure Security Agency (CISA), as well as selected resources from Red Hot Cyber and other international sources.

National Vulnerability Database Information

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

CVSS Base Score: 9.8 (v3.1)

The **CVSS Base Score** is a score from **0 to 10** that represents the intrinsic severity of a vulnerability. A higher score indicates greater severity.

Value
0.02.55.07.510.0
Published on: 09/07/2021 17:15:07
Last modified: 11/05/2025 19:13:20
NIST: CVE source from the National Vulnerability Database (NVD)

CVSS Metrics Details

  • Base Severity: CRITICAL
  • Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  • Attack Vector: NETWORK
  • Attack Complexity: LOW
  • Privileges Required: NONE
  • User Interaction: NONE
  • Scope: UNCHANGED
  • Confidentiality Impact: HIGH
  • Integrity Impact: HIGH
  • Availability Impact: HIGH

Common Weakness Enumeration (CWE)

Database CWE: v4.18

CWE-706: Use of Incorrectly-Resolved Name or Reference ↗

The product uses a name or reference to access a resource, but the name/reference resolves to a resource that is outside of the intended control sphere.

Fonte: MITRE CWE


FIRST Information

EPSS Score: 0.9442

The **EPSS (Exploit Prediction Scoring System)** is a score from **0 to 1** that indicates the **probability** that a vulnerability will be exploited in the real world in the next 30 days. A higher value indicates a greater likelihood of exploitation.

Value
0.00.250.50.751.0

Percentile: 0.9998

The **Percentile** indicates how much higher this vulnerability's EPSS score is compared to all other vulnerabilities in the EPSS database. For example, a percentile of 0.90 (90%) means that 90% of vulnerabilities have an EPSS score equal to or lower than the current one.

Value
0.00.250.50.751.0

*Data updated as of: 2025-12-12


CISA Information (Known Exploited Vulnerabilities)

The **CISA KEV Catalog** lists vulnerabilities that have been **actively exploited in the real world**. If a CVE is present in this catalog, it indicates that the threat is immediate and mitigation should be a top priority.

CVE **CVE-2021-40539** **IS PRESENT** in the CISA KEV Catalog!

  • Vulnerability Name: Zoho ManageEngine ADSelfService Plus Authentication Bypass Vulnerability
  • Short Description: Zoho ManageEngine ADSelfService Plus contains an authentication bypass vulnerability affecting the REST API URLs which allow for remote code execution.
  • Date Added to KEV: 11/03/2021
  • Vendor/Product: Zoho / ManageEngine
  • Required Action: Apply updates per vendor instructions.
  • Due Date: 11/17/2021

Articles published on Red Hot Cyber


NVD References

Exploit PoC from GitHub