Strobes VIStrobes VI
CVE DatabaseThreat ActorsResearchAPI Docs
Visit Strobes.coSign Up for Strobes
CVE DatabaseThreat ActorsResearchAPI Docs
Tools
KB Lookup
Visit Strobes.coSign Up for Strobes
HomeCVEs

Do you like the insights?

Strobes vulnerability intelligence is a key component of their Exposure Management platform that helps organizations understand, prioritize, and address security vulnerabilities more effectively.

© 2026 Strobes Security. All rights reserved.
HomeCVEsCVE-2021-40539

CVE-2021-40539

Published: January 27, 2026
Last updated:14 hours ago (January 27, 2026)
Exploit: YesZero-day: YesPatch: YesTrend: Neutral
TL;DR
Updated January 27, 2026

CVE-2021-40539 is a critical severity vulnerability with a CVSS score of 9.8. Exploits are available; patches have been released and should be applied urgently. This is classified as a zero-day vulnerability.

Key Points
  • 1Critical severity (CVSS 9.8/10)
  • 2EPSS: 94.00% - very high likelihood of exploitation
  • 3Public exploits are available
  • 4Vendor patches are available
  • 5Strobes Priority Score: 928/1000 (Critical)
  • 6Affects products from: Zohocorp
Severity Scores
CVSS v39.8
CVSS v27.5
Priority Score928.0
EPSS Score94.0
Critical
Exploitation LikelihoodCritical
94.00%EPSS

Very high probability of exploitation in the next 30 days

Immediate patching required
94.00%
EPSS
9.8
CVSS
Yes
Exploit
Yes
Patch
Critical Priority
high EPSS • exploit exists • critical severity • high priority

EPSS predicts the probability of exploitation in the next 30 days based on real-world threat data, complementing CVSS severity scores with actual risk assessment.

Description

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

CVSS v3 Breakdown
Attack Vector:Network
Attack Complexity:Local
Privileges Required:Network
User Interaction:Network
Scope:Unchanged
Confidentiality:High
Integrity:High
Availability:High
Exploit References
Cisa.govPacketstormsecurity.comMetasploitGitHubGitHubGitHubGitHubGitHubNucleiGitHub
Patch References
[email protected]Zeroday CZ
Trend Analysis
Neutral
Vulnerable Products
VendorProduct
ZohocorpManageengine Adselfservice Plus
Advisories
CISA: Zoho ManageEngine ADSelfService Plus contains an authentication bypass vulnerability affecting the REST API URLs which allow for remote code execution.
GitHub AdvisoryNVD
Cite This Page
APA Format
Strobes VI. (2026). CVE-2021-40539 - CVE Details and Analysis. Strobes VI. Retrieved January 27, 2026, from https://vi.strobes.co/cve/CVE-2021-40539
Quick copy link + title

Please cite this page when referencing data from Strobes VI. Proper attribution helps support our vulnerability intelligence research.