SOC status:Duty analyst on shift

UK Cyber Defence
VulnerabilityAnalyzed

CVE-2021-40539

Zoho ManageEngine ADSelfService Plus Authentication Bypass Vulnerability

KEVCRITICAL 9.8EPSS 99.0%

Does this matter?

Known to be exploited in the wild (CISA KEV, CISA remediation deadline 17 November 2021). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.

Description

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

CVSS 3.1
9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
98.96% probability · 100th percentile
Public exploits
None in Exploit-DB
CISA KEV
Listed 3 November 2021 · due 17 November 2021 · used in ransomware campaigns
Weakness
CWE-706
Affected
zohocorp/manageengine adselfservice plus
Source
cve@mitre.org
EPSS trend
0%50%100%30 October 2026: 98.96%30 October 202630 October 2026

EPSS 99.0% since 30 October 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.

CISA notes

Apply updates per vendor instructions. https://nvd.nist.gov/vuln/detail/CVE-2021-40539

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.