How severe is CVE-2021-40539?

CVE-2021-40539 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-40539 being actively exploited?

Yes. CVE-2021-40539 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2021-11-03, which means active exploitation has been confirmed. It should be prioritised for remediation.

What products are affected by CVE-2021-40539?

CVE-2021-40539 primarily affects Zohocorp Manageengine Adselfservice Plus. In total, 10 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-40539?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.

Does CVE-2021-40539 have an EU (EUVD) identifier?

Yes. CVE-2021-40539 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-27714. It is also flagged as exploited in the EUVD (since 2021-11-03).

When was CVE-2021-40539 published?

CVE-2021-40539 was published on 2021-09-07 and last updated on 2026-06-17.

CVE-2021-40539

CVE-2021-40539 is a critical-severity vulnerability in Zohocorp Manageengine Adselfservice Plus with a CVSS 3.x base score of 9.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2021-11-03). The underlying weakness is classified as CWE-706.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 99% (100th percentile)
Actively exploited: Yes — listed in CISA KEV (added 2021-11-03)
EU (EUVD) id: EUVD-2021-27714
EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2021-11-03)
Weakness: CWE-706
Affected product: Zohocorp Manageengine Adselfservice Plus
Published: 2021-09-07
Last modified: 2026-06-17

Description

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

Frequently asked questions

What is CVE-2021-40539?: Zoho ManageEngine ADSelfService Plus version 6113 and prior is vulnerable to REST API authentication bypass with resultant remote code execution.
How severe is CVE-2021-40539?: CVE-2021-40539 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-40539 being actively exploited?: Yes. CVE-2021-40539 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2021-11-03, which means active exploitation has been confirmed. It should be prioritised for remediation.
What products are affected by CVE-2021-40539?: CVE-2021-40539 primarily affects Zohocorp Manageengine Adselfservice Plus. In total, 10 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-40539?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.
Does CVE-2021-40539 have an EU (EUVD) identifier?: Yes. CVE-2021-40539 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-27714. It is also flagged as exploited in the EUVD (since 2021-11-03).
When was CVE-2021-40539 published?: CVE-2021-40539 was published on 2021-09-07 and last updated on 2026-06-17.

References

Affected products (10)

cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:*:*:*:*:*:*:*:*
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:6.1:-:*:*:*:*:*:*
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:6.1:6100:*:*:*:*:*:*
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:6.1:6101:*:*:*:*:*:*
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:6.1:6102:*:*:*:*:*:*
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:6.1:6103:*:*:*:*:*:*
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:6.1:6104:*:*:*:*:*:*
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:6.1:6105:*:*:*:*:*:*
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:6.1:6106:*:*:*:*:*:*
cpe:2.3:a:zohocorp:manageengine_adselfservice_plus:6.1:6113:*:*:*:*:*:*

More vulnerabilities in Zohocorp Manageengine Adselfservice Plus

CVE-2019-3905 — Critical (CVSS 10.0): Zoho ManageEngine ADSelfService Plus 5.x before build 5703 has SSRF.
CVE-2023-35854 — Critical (CVSS 9.8): Zoho ManageEngine ADSelfService Plus through 6113 has an authentication bypass that can be exploited to steal the…
CVE-2022-47966 — Critical (CVSS 9.8): Multiple Zoho ManageEngine on-premise products, such as ServiceDesk Plus through 14003, allow remote code execution due…
CVE-2021-37422 — Critical (CVSS 9.8): Zoho ManageEngine ADSelfService Plus 6111 and prior is vulnerable to SQL Injection while linking the databases.
CVE-2021-37423 — Critical (CVSS 9.8): Zoho ManageEngine ADSelfService Plus 6111 and prior is vulnerable to linked applications takeover.
CVE-2021-37421 — Critical (CVSS 9.8): Zoho ManageEngine ADSelfService Plus 6103 and prior is vulnerable to admin portal access-restriction bypass.

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