Authentication Bypass and RCE in Zoho ManageEngine ADSelfService Plus
CVE-2021-40539 is a critical vulnerability in Zoho ManageEngine ADSelfService Plus affecting builds up to 6113. The flaw resides in REST API URL handling, where an error in URL normalization before validation allows specially crafted requests such as variants of REST API paths to bypass the product’s authentication security filter. By reaching protected REST API endpoints without valid authentication, an attacker can trigger follow-on actions that result in arbitrary command execution and remote code execution. Public reporting and vendor/advisory material indicate exploitation involved uploading a ZIP containing a JSP webshell disguised as an x509 certificate file (for example, service.cer), after which the webshell could be accessed from application paths such as /help/admin-guide/Reports/ReportGenerate.jsp. The issue was fixed in build 6114.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
2 valid exploits after Mallory filtered fakes, detection scripts, and README-only repos (1 hidden).
This repository contains a Python exploit script (exploit.py) targeting CVE-2021-40539, a critical authentication bypass and RCE vulnerability in ManageEngine ADSelfService Plus. The exploit works by uploading a JSP webshell and/or a malicious Java class to the vulnerable server via the '/./RestAPI/LogonCustomization' endpoint, then triggering remote code execution through the '/./RestAPI/Connection' endpoint. The script can optionally verify if the target is vulnerable before exploitation. If successful, the attacker gains a webshell at '/help/admin-guide/test.jsp', allowing arbitrary command execution. The repository is structured with a single exploit script and a README referencing external exploitation details. The exploit is operational, providing a working payload and automated exploitation steps.
This repository contains a Python exploit script (CVE-2021-40539.py) targeting Zoho ManageEngine ADSelfService Plus (version 6113 and earlier) for CVE-2021-40539, a critical authentication bypass and remote code execution vulnerability. The script allows both single-target and batch exploitation. It first checks if the target is vulnerable by sending a crafted POST request to the '/./RestAPI/LogonCustomization' endpoint. If vulnerable, it uploads a JSP webshell and a Java class file (either user-supplied or a default payload) to the same endpoint. The exploit then triggers RCE by sending a POST request to '/./RestAPI/Connection', leveraging the uploaded Java class. Finally, it verifies the webshell at '/help/admin-guide/test.jsp', which can be used to execute arbitrary commands on the target system. The repository also includes a README.md with usage instructions and background on the vulnerability. The exploit is operational, providing a working RCE chain with persistent access via the webshell.
Affected products & vendors
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
13 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An unpatched critical vulnerability in an authentication module that was exploited to gain access to servers hosting sensitive personal data in the ICRC/Red Cross breach.
A vulnerability (unspecified in the content) affecting Zoho ManageEngine ADSelfService that is listed as exploited by the threat actor UNC3886/Volt Typhoon.
A critical vulnerability in Zoho ManageEngine ADSelfService Plus referenced as being exploited in a cyberespionage campaign.
A critical authentication bypass vulnerability in ManageEngine ADSelfService Plus REST API URL handling that can lead to remote code execution via crafted URLs that bypass security filtering.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.