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CVE-2021-40539

98
FAUCET Score

CVE-2021-40539 is a critical REST API authentication bypass vulnerability affecting Zoho ManageEngine ADSelfService Plus version 6113 and prior, leading to remote code execution. With a CVSS score of 9.8, this vulnerability is easily exploitable over the network without authentication, allowing attackers full control over affected systems. It is actively exploited in the wild, including by known ransomware campaigns and state-backed APTs, with public exploit modules available in Metasploit and Nuclei. The vulnerability has garnered significant community discussion and media attention, highlighting its severe risk.

Impacted Technologies

VendorProductVersion(s)CPE
< 6.1CPE matchmatch criteria
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:*:*:*:*:*:*:*:*
6.1CPE matchmatch criteria
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:6.1:-:*:*:*:*:*:*
6.1CPE matchmatch criteria
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:6.1:6100:*:*:*:*:*:*
6.1CPE matchmatch criteria
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:6.1:6101:*:*:*:*:*:*
6.1CPE matchmatch criteria
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:6.1:6102:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
98.96%
Probability of exploitation in next 30 days
EPSS Percentile
99.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-25
Model: v2026.06.15
Added to KEV · Nov 3, 2021
Metasploit: ManageEngine ADSelfService Plus CVE-2021-40539 · Sep 7, 2021
Nuclei: CVE-2021-40539 · Sep 16, 2021
This CVE's current EPSS score of 0.9896 is in the 100th percentile among its peer group of 36,833 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

cisa.gov / known-exploited-vulnerabilities-catalog
US Government Resource
packetstormsecurity.com / files/165085/ManageEngine-ADSelfService-Plus-Authentication-Bypass-Code-Execution.html
ExploitThird Party AdvisoryVDB Entry
manageengine.com
Product
manageengine.com / products/self-service-password/kb/how-to-fix-authentication-bypass-vulnerability-in-REST-API.html
PatchVendor Advisory