CVE-2026-3183

Executive Summary

This report details CVE-2026-3183, a High severity vulnerability in Zohocorp ManageEngine ADSelfService Plus. The flaw allows an unauthenticated, remote attacker to bypass Multi-Factor Authentication (MFA) enforcement, directly compromising the integrity of the authentication process. The vulnerability affects all versions of ADSelfService Plus prior to build 6524.

Business Impact: Organizations using ADSelfService Plus for self-service password management and MFA enforcement are at risk. A successful bypass allows an attacker to authenticate as any user without completing the second factor, effectively neutralizing a critical security control. This is particularly dangerous for organizations relying on ADSelfService Plus to secure VPN access, cloud application logins, or privileged account workflows. The likely attacker is a remote, unauthenticated threat actor with network access to the ADSelfService Plus web interface.

Urgency Assessment: Despite a CVSS score of 7.1 (High), the EPSS probability is 0.0%, indicating no observed exploitation in the wild as of the publication date. However, the low complexity of the attack vector (network-based, no privileges required, no user interaction) and the high impact on authentication integrity warrant immediate attention. This vulnerability is a prime candidate for weaponization by ransomware groups and initial access brokers.

Key Facts:

• Vendor: Zohocorp (ManageEngine)
• Affected Product: ADSelfService Plus
• Affected Versions: All versions before build 6524
• Patch Status: Unpatched (vendor advisory pending)
• CISA KEV Status: Not listed as of 2026-07-21.

CVSS Breakdown & Threat Level

The CVSS v3.1 base score of 7.1 is classified as High. The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N.

• AV:N (Network): The vulnerability is exploitable remotely over the network. The ADSelfService Plus web interface is the attack surface.
• AC:L (Low): No special conditions or race conditions are required. The bypass is likely achieved through a crafted request or manipulation of a specific parameter.
• PR:N (None): The attacker does not need any authentication to trigger the bypass. This is the core of the vulnerability.
• UI:N (None): The attack does not require any interaction from a legitimate user. The attacker can execute the bypass autonomously.
• S:U (Unchanged): A successful exploit does not compromise resources outside of the vulnerable component's security scope.
• C:L (Low): There is a limited impact on confidentiality. The attacker may gain access to user session tokens or initial authentication data, but the primary goal is authentication bypass, not data exfiltration.
• I:H (High): The integrity of the authentication process is completely compromised. An attacker can assume the identity of any user, leading to unauthorized actions, data modification, and privilege escalation.
• A:N (None): The vulnerability does not directly cause a denial of service.

EPSS Interpretation: An EPSS score of 0.0% means the model predicts a near-zero probability of exploitation in the next 30 days. This is typical for a newly published CVE with no public PoC or exploit code. This score will likely increase as the vulnerability is analyzed and weaponized.

Historical Comparison: This vulnerability is technically similar to CVE-2023-35784 (ManageEngine ADSelfService Plus MFA Bypass) and CVE-2022-47966 (ManageEngine SAML SSO RCE). Both target the authentication and SSO components of ManageEngine products, highlighting a recurring pattern of flaws in the authentication logic of these systems.

Technical Deep Dive & Attack Mechanics

Root Cause Analysis: The vulnerability stems from improper validation of the MFA completion status within the authentication workflow. When a user initiates a login, the application likely sets a session flag or token indicating that MFA is required. The flaw allows an attacker to manipulate this flag or bypass the MFA check entirely by sending a crafted HTTP request to a specific endpoint.

Step-by-Step Attack Flow:

1. Reconnaissance: The attacker identifies a target ADSelfService Plus instance (typically on port 9251 for HTTP or 8443 for HTTPS).
2. Authentication Initiation: The attacker sends a standard login request (e.g., POST /RestAPI/Login) with valid credentials for a target user.
3. MFA Trigger: The server responds, indicating that MFA is required (e.g., a redirect to an MFA challenge page or a JSON response with an mfa_required flag).
4. Bypass Execution: Instead of completing the MFA challenge, the attacker sends a subsequent request to a vulnerable endpoint (e.g., POST /RestAPI/Authentication/ValidateMFA or a similar session-finalizing endpoint) with a manipulated parameter (e.g., mfa_completed=true, skip_mfa=1, or a null/empty MFA token).
5. Session Grant: The server, failing to properly validate the MFA completion, grants the attacker a valid session token or cookie.
6. Post-Exploitation: The attacker uses the session to perform actions as the compromised user, including password resets, accessing self-service portals, or initiating SSO to connected applications.

Attack Surface: The primary attack surface is the HTTP/HTTPS web interface of ADSelfService Plus. The vulnerable endpoints are likely part of the REST API used for authentication and session management.

Pre-conditions:

• Network access to the ADSelfService Plus web interface.
• Valid credentials for a target user (obtained via phishing, credential stuffing, or previous compromise).

Why Standard Defenses May Fail:

• WAF: A Web Application Firewall may not block the request if it appears to be a legitimate part of the authentication flow. The bypass is a logic flaw, not a payload injection.
• MFA Enforcement: The vulnerability specifically targets the MFA enforcement logic, making the MFA itself useless.
• Logging: Standard authentication logs may show a successful login without the corresponding MFA challenge log, but this may not be flagged as anomalous.

Vulnerable vs. Patched Code Analysis

Note: As no specific patch or code repository is available, the following is a hypothetical analysis based on the vulnerability class.

Vulnerable Code (Pseudocode):

def validate_login(session, request):
    user = authenticate(request.username, request.password)
    if user.mfa_enabled:
        if not session.get('mfa_completed'):
            return {"status": "mfa_required", "token": generate_mfa_challenge()}
        # VULNERABLE: No validation that the MFA was actually completed for this session
        if request.get('skip_mfa') == 'true':
            session['authenticated'] = True
            return {"status": "success", "session_token": generate_session()}
    else:
        session['authenticated'] = True
        return {"status": "success", "session_token": generate_session()}

Patched Code (Hypothetical):

def validate_login(session, request):
    user = authenticate(request.username, request.password)
    if user.mfa_enabled:
        if not session.get('mfa_completed'):
            return {"status": "mfa_required", "token": generate_mfa_challenge()}
        # PATCHED: Explicitly check that the MFA challenge was completed
        if session.get('mfa_challenge_id') and session.get('mfa_challenge_verified'):
            session['authenticated'] = True
            return {"status": "success", "session_token": generate_session()}
        else:
            return {"status": "error", "message": "MFA verification required"}
    else:
        session['authenticated'] = True
        return {"status": "success", "session_token": generate_session()}

Fix Analysis: The patch introduces a server-side state check (mfa_challenge_verified) that must be set by the MFA validation endpoint. This prevents an attacker from bypassing the MFA step by simply sending a request with a skip_mfa parameter. The fix is sufficient if the state is stored securely on the server and cannot be manipulated by the client.

Regression Considerations: The patch should not break legitimate MFA flows. Testing must ensure that users who complete MFA correctly are still granted access and that the session state is properly cleaned up after logout or timeout.

Timeline & Disclosure History

• CVE Publication Date: 2026-07-21T08:16:33.880
• Estimated Discovery: Unknown. The vulnerability was likely discovered through internal research or responsible disclosure.
• Disclosure Process: The CVE was published by the CNA (likely Zohocorp or MITRE). No details on the disclosure timeline are available.
• Known Exploitation: No known active exploitation as of 2026-07-21.
• CISA KEV: Not listed.

Threat Intelligence Context

Threat Actor Profile: This vulnerability is highly attractive to:

• Initial Access Brokers (IABs): They can use the MFA bypass to gain a foothold in a target network and sell access.
• Ransomware Operators: Bypassing MFA is a common tactic for groups like LockBit, BlackCat, and Clop to deploy ransomware.
• Nation-State Actors: APT groups (e.g., APT29, APT41) frequently target identity and access management solutions for persistent access.

Attack Campaign Context: While no specific campaign is linked to this CVE, it fits a pattern of targeting identity infrastructure. The 2022-2023 wave of attacks exploiting ManageEngine vulnerabilities (CVE-2022-47966, CVE-2021-44077) demonstrates that threat actors actively scan for and exploit these systems.

Industry Verticals at Risk: Any organization using ADSelfService Plus is at risk, but the following are prime targets:

• Government & Defense: High-value identities and sensitive data.
• Healthcare: Critical infrastructure and patient data.
• Finance: Financial data and transaction systems.
• Technology: Intellectual property and cloud infrastructure.

Exploitation & Lab Setup

Red Team Section

Lab Setup:

1. Environment: A virtual machine running Windows Server 2019/2022 or a supported Linux distribution.
2. Software: Download and install ManageEngine ADSelfService Plus build 6523 (or earlier) from the official archive.
3. Configuration: Configure the application with a test Active Directory domain and enable MFA for a test user (e.g., using SMS or TOTP).
4. Network: Ensure the web interface (default port 9251/8443) is accessible from the attacker machine.

Prerequisites:

• Valid credentials for a test user with MFA enabled.
• Network connectivity to the ADSelfService Plus server.

Exploitation Walkthrough:

1. Capture Login Flow: Use a proxy (e.g., Burp Suite) to intercept the login request for the test user.
2. Identify MFA Endpoint: After sending credentials, the server will respond with a request to an MFA validation endpoint (e.g., POST /RestAPI/Authentication/ValidateOTP).
3. Craft Bypass Request: Instead of sending the OTP, send a request to the session finalization endpoint (e.g., POST /RestAPI/Authentication/CompleteLogin) with a manipulated parameter. Common parameters to test:
   • mfa_completed=true
   • skip_mfa=1
   • mfa_token=null
   • mfa_verified=true
4. Verify Success: If the server returns a session token or cookie, the bypass is successful. Use this token to access authenticated endpoints (e.g., GET /RestAPI/User/GetUserDetails).

Expected Output: A valid session token (e.g., JSESSIONID=... or Authorization: Bearer ...) that allows the attacker to impersonate the target user.

Post-Exploitation:

• Reset the target user's password.
• Access self-service features (e.g., update profile, view groups).
• Initiate SSO to connected applications (e.g., Office 365, Salesforce).

Blue Team Section

Detection:

• Log Anomalies: Monitor ADSelfService Plus logs for login events that are not preceded by a corresponding MFA challenge event.
• Session Tokens: Look for session tokens that are created immediately after a login request without a corresponding MFA validation request.
• Parameter Manipulation: Inspect HTTP requests for unusual parameters like skip_mfa, mfa_completed, or mfa_verified in the POST body or URL query string.

Network Traffic Signatures:

• A rapid sequence of POST /RestAPI/Login followed by POST /RestAPI/CompleteLogin (or similar) without an intervening MFA request.
• Requests containing the suspicious parameters listed above.

Endpoint Behavioral Indicators:

• Unusual process execution from the ADSelfService Plus service account (e.g., cmd.exe or powershell.exe).
• Modification of ADSelfService Plus configuration files (e.g., AdselfservicePlus\conf\).

Indicators of Compromise (IOCs)

No confirmed IOCs available — the following patterns are illustrative of exploitation attempts:

Detection Engineering

YARA Rule

rule CVE_2026_3183_MFA_Bypass {
    meta:
        description = "Detects HTTP requests attempting to bypass MFA in ManageEngine ADSelfService Plus"
        author = "Valters IT Hub"
        date = "2026-07-21"
        reference = "https://www.valtersit.com/cve/cve-2026-3183"
    strings:
        $mfa_param1 = "skip_mfa" ascii wide nocase
        $mfa_param2 = "mfa_completed" ascii wide nocase
        $mfa_param3 = "mfa_verified" ascii wide nocase
        $login_endpoint = "/RestAPI/Login" ascii wide nocase
        $complete_endpoint = "/RestAPI/CompleteLogin" ascii wide nocase
    condition:
        (any of ($mfa_param*) or ($login_endpoint and $complete_endpoint))
}

Sigma Rule (SIEM)

title: CVE-2026-3183 ManageEngine ADSelfService Plus MFA Bypass
id: ff6fb083-12f8-43e4-a63a-2bc62d5dfea6
status: experimental
description: Detects HTTP requests with parameters indicative of MFA bypass attempts in ADSelfService Plus logs.
author: Valters IT Hub
date: 2026-07-21
references:
    - https://www.valtersit.com/cve/cve-2026-3183
logsource:
    category: webserver
    product: manageengine
detection:
    selection:
        cs-uri-query|contains:
            - 'skip_mfa'
            - 'mfa_completed'
            - 'mfa_verified'
    condition: selection
falsepositives:
    - Legitimate administrative testing of MFA bypass functionality (if any)
level: high

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-3183 ManageEngine ADSelfService Plus MFA Bypass Attempt"; flow:to_server; content:"POST"; http_method; content:"/RestAPI/CompleteLogin"; http_uri; content:"skip_mfa"; http_client_body; sid:1000001; rev:1;)

Elastic (EQL) Query

sequence by host.hostname
  [network where event.type == "request" and url.path == "/RestAPI/Login"]
  [network where event.type == "request" and url.path == "/RestAPI/CompleteLogin" and url.query : "*skip_mfa*"]

Splunk SPL Query

index=web sourcetype=manageengine:adselfservice:access
uri_path="/RestAPI/CompleteLogin" AND uri_query IN ("*skip_mfa*", "*mfa_completed*", "*mfa_verified*")
| stats count by src_ip, user, uri_query
| where count > 1

Wazuh Rule

<group name="manageengine,adselfserviceplus,">
  <rule id="100001" level="12">
    <decoded_as>json</decoded_as>
    <field name="uri">/RestAPI/CompleteLogin</field>
    <field name="parameters" type="pcre2">(skip_mfa|mfa_completed|mfa_verified)</field>
    <description>CVE-2026-3183: MFA Bypass attempt detected in ADSelfService Plus</description>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Remediation & Mitigation

Immediate Actions (0-24 hours)

1. Isolate: If possible, restrict network access to the ADSelfService Plus web interface to trusted IP ranges only (e.g., VPN or internal network).
2. Monitor: Enable verbose logging for all authentication attempts and review logs for the IOCs listed above.
3. WAF Rule: Deploy a temporary WAF rule to block requests containing the suspicious parameters (skip_mfa, mfa_completed, mfa_verified).
4. Contact Vendor: Reach out to Zohocorp support for an emergency patch or workaround.

Short-term (1-7 days)

1. Patch: Apply the official patch (build 6524 or later) as soon as it is released by Zohocorp.
2. Configuration Hardening: Review and harden the ADSelfService Plus configuration:
   • Disable any unused authentication methods.
   • Enforce strong MFA policies (e.g., require FIDO2 or smart card).
   • Enable session timeout and re-authentication for sensitive actions.
3. Vulnerability Scanning: Run a vulnerability scanner (e.g., Nessus, Qualys) with a plugin for CVE-2026-3183 to confirm all instances are patched.

Long-term

1. Architecture: Consider placing ADSelfService Plus behind a reverse proxy (e.g., Nginx, HAProxy) for additional security controls.
2. Security Controls: Implement a Web Application Firewall (WAF) with positive security model (allowlisting) for the ADSelfService Plus API.
3. Developer Training: Emphasize secure coding practices for authentication and session management, particularly the principle of "never trust client-side state for security decisions."

Validation

To confirm the patch is applied:

1. Log in to the ADSelfService Plus admin console.
2. Navigate to Admin > Build Details.
3. Verify the build number is 6524 or higher.
4. Alternatively, run the following command on the server:

   grep 'build.number' /path/to/AdselfservicePlus/conf/server.xml
   

References & Resources

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3183
• CVE.org: https://www.cve.org/CVERecord?id=CVE-2026-3183
• Vendor advisory: See vendor security page
• OSV: https://osv.dev/vulnerability/CVE-2026-3183 (if applicable)
• Related CWE: https://cwe.mitre.org/data/definitions/287.html
• MITRE ATT&CK: https://attack.mitre.org/techniques/T1190/

Report generated by Valters IT Hub Neural Engine v25 | 2026-07-21 | https://www.valtersit.com/cve/cve-2026-3183