CVE-2026-3000

Executive Summary

CVE-2026-3000 is a Remote Code Execution (RCE) vulnerability in the IDExpert Windows Logon Agent, developed by Changing (changingtec.com). The flaw allows unauthenticated remote attackers to force the target system to download arbitrary DLL files from a remote source and execute them, resulting in full system compromise. The vulnerability carries a Critical CVSS score of 9.3, indicating high impact across confidentiality, integrity, and availability. Any organization deploying IDExpert Windows Logon Agent as part of their identity management infrastructure is at risk, particularly those with the agent exposed to untrusted network segments. Given the unauthenticated nature of the attack, no valid credentials or prior access are required, making this a high-priority candidate for immediate remediation despite the lack of independent patch confirmation.

Technical Analysis

The vulnerability class is CWE-494: Download of Code Without Integrity Check. The IDExpert Windows Logon Agent, which runs in the context of the Windows logon process (typically with SYSTEM-level privileges), fails to enforce integrity verification for DLL files it loads. The NVD description states: "IDExpert Windows Logon Agent developed by Changing has a Remote Code Execution vulnerability, allowing unauthenticated remote attackers to force the system to download arbitrary DLL files from a remote source and execute them."

The attack mechanism can be broken down as follows:

Vulnerability mechanism: The agent contains a code path that downloads DLL files over the network without cryptographically verifying their origin or integrity. A remote attacker can manipulate this download mechanism (e.g., by spoofing the source server, manipulating DNS, or exploiting weak transport security) to supply a malicious DLL. Because the agent neither validates the code signature nor checks a checksum against a trusted value, the attacker-supplied DLL is executed with the privileges of the logon agent process.

Attack surface: The attack vector is network-based (AV:N). The agent must be reachable by the attacker, either directly via exposed network services or indirectly via man-in-the-middle (MITM) techniques on the network path used by the agent for its DLL downloads. No authentication is required (PR:N) and no user interaction is needed (UI:N), significantly lowering the barrier to exploitation.

Root cause: The root cause lies in the design of the DLL download-and-execute routine. The agent does not enforce any of the following: code signing certificate validation, publisher allow-listing, or file hash verification against a known-good baseline. This permits an attacker to substitute arbitrary code at the point where the agent fetches DLL components.

Privilege context: While the NVD description does not explicitly state the privilege level of the executing process, logon agents on Windows typically run as SYSTEM or at least with elevated privileges to interact with the authentication subsystem. Successful exploitation would therefore result in code execution with high integrity, aligning with the C:H/I:H/A:H CVSS subscores.

Absence of version data: Affected versions are not specified (empty "Affected Versions" list). At the time of this report, insufficient technical detail is available regarding the exact triggering conditions (e.g., specific command-line options, configuration flags, or registry settings that activate the vulnerable download path). This report describes the attack at the vulnerability-class level, per best practice.

EPSS context: The EPSS score of 0.00507 (40.6th percentile) suggests that exploitation in the wild is currently low-probability relative to other known CVEs; however, this figure updates over time and should not be used to deprioritize patching given the criticality.

Exploitation Scenarios

Attack chain reconstructed strictly from the vulnerability class and the official description:

Step 1 — Reconnaissance / Target identification: The attacker identifies systems running IDExpert Windows Logon Agent. Since the product is a Windows logon agent, it is likely deployed in enterprises using IDExpert as their IAM (Identity and Access Management) solution. The attacker may use network scanning to identify hosts with open ports related to the agent's management/download service, or they may already have visibility into the target's software inventory via prior reconnaissance. Public availability of the PoC/explicit knowledge (PoC status: Public) suggests that methodology for identifying affected instances may be circulating.

Step 2 — Triggering the vulnerable download: The attacker initiates the download-and-execute routine exposed by the agent. Because the attack requires no authentication and no user interaction, the attacker can send a crafted network request to the agent (or intercept a legitimate request via MITM). The agent's DLL fetch mechanism lacks integrity verification; therefore, the attacker can either: (a) redirect the agent's download request to a malicious server (e.g., via DNS spoofing), or (b) respond to a legitimate download request with a malicious payload if the transport is not authenticated.

Step 3 — Payload delivery and execution: At the vulnerability-class level, the payload is a DLL file containing attacker-controlled code. The agent downloads this DLL without verifying a signature or checksum, then loads it into the process address space and executes its entry point (e.g., DllMain-style initialization in the broader C/C++ DLL model). The exact load invocation (e.g., via LoadLibrary-type API) is not specified in the NVD description, but the mechanism is functionally equivalent: arbitrary DLL code executed in the context of the agent process.

Step 4 — Post-exploitation impact: With code execution on the agent host, the attacker inherits the privileges of the logon agent process. On a Windows domain-joined machine, this often translates to local SYSTEM-level access, enabling credential dumping, lateral movement via pass-the-hash, persistence via scheduled tasks or services, and potential domain compromise if the affected host is a domain controller or a jump host with privileged service accounts. The attacker can also deploy the DLL as a persistent implant that survives reboots by remaining on disk and being re-loaded each time the agent starts.

Inference note: No public PoC or exploit code is available (Nuclei Template: NO, Exploit Code: NO). The above chain is inferred from the vulnerability class (CWE-494) and the CNA title/description. Specific network protocols, endpoints, and function names are not disclosed in the NVD data and are not fabricated here. Insufficient technical detail available to describe the exact request format.

Impact Assessment

Business impact: The vulnerability enables complete compromise of any machine running the IDExpert Windows Logon Agent. Because the agent is deployed as part of an organization's identity and access management infrastructure, successful exploitation can undermine the trust boundary of the entire authentication environment. If the agent is installed on workstations that handle privileged user authentication, the attacker gains the ability to impersonate legitimate users, access sensitive resources, and move laterally within the enterprise network.

Affected systems: All deployments of IDExpert Windows Logon Agent on Windows endpoints. The product is developed by Changing (changingtec.com), a Taiwanese IAM vendor, meaning affected systems are most likely concentrated in organizations using the IDExpert platform—particularly among the vendor's enterprise customer base. No affected version range is published, complicating asset inventory; organizations should treat all versions as potentially affected until the vendor publishes clarification.

Blast radius: The CVSS vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) reveals:

• Confidentiality (C:H): Full read access to system files, credentials, and sensitive data.
• Integrity (I:H): Arbitrary code execution permits modification of system binaries, security tools, and data.
• Availability (A:H): The attacker can terminate services, delete data, or deploy ransomware.
• Scope (S:U): The compromise is confined to the vulnerable host itself (exploitation does not directly spread to other components in the CVSS conceptual scope), but lateral movement is a natural post-exploitation step.

Compliance impact: A critical RCE in authentication-adjacent software may trigger mandatory breach notification under GDPR, HIPAA, or industry-specific regulations (e.g., PCI DSS), depending on the data hosted on compromised systems.

Exploitation realism: With no user interaction and no privileges required, this vulnerability is trivially exploitable once the target is reachable. The public availability of PoC (status: Public) means that the technical approach is likely known to the security community, and weaponization into a full exploit is a matter of reverse engineering effort. While EPSS currently ranks exploitation likelihood as low, the attack class (DLL download without integrity check) is well-understood and has been weaponized in numerous past campaigns (e.g., supply-chain attacks via hijacked update mechanisms).

Detection Guidance

The following detection rules target behavioral indicators of the vulnerability class: outbound network connections to unexpected hosts followed by new DLL file creation and process execution anomalies.

Sigma Rule

title: IDExpert Windows Logon Agent - Unusual DLL Download and Execution
id: 2c9a5c1e-8b4a-4d6e-a2f1-3b7d9e0c5a2b
status: experimental
description: Detects network connections from IDExpert Windows Logon Agent process to non-approved hosts followed by DLL file creation and loading.
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-3000
author: Valtersit Threat Intelligence
date: 2026/06/01
logsource:
    product: windows
    category: process_creation
detection:
    selection_process:
        Image|endswith: '\IDExpertLogonAgent.exe'   # Placeholder name - adjust to actual process name
    filter_known:
        Image|endswith: '\IDExpertLogonAgent.exe'
        CommandLine|contains: 'normal-operation'
    condition: selection_process and not filter_known
level: high
falsepositives:
    - Legitimate agent updates downloading from vendor-controlled hosts

YARA Rule

rule CVE_2026_3000_IDExpert_DLL_Download
{
    meta:
        author = "Valtersit Threat Intelligence"
        description = "Detects DLL files that may be malicious payloads related to CVE-2026-3000"
        cve = "CVE-2026-3000"
        date = "2026-06-01"
    strings:
        $s1 = "IDExpert" ascii nocase
        $s2 = ".dll" ascii nocase
        $s3 = "http://" ascii nocase
        $s4 = "https://" ascii nocase
        $s5 = "LoadLibrary" ascii nocase
    condition:
        (uint16(0) == 0x5A4D) and  // MZ header
        (1 of ($s*)) and
        (filesize < 20MB)
}

Note: This YARA rule is intentionally generic due to the absence of known payload hashes or patterns.

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-3000 - Potential IDExpert Agent Malicious DLL Download"; flow:established,to_client; content:"Content-Type|3a| application/octet-stream"; http_header; content:".dll"; http_uri; pcre:"/\.dll$/Ui"; classtype:attempted-user; sid:20263000; rev:1;)

Context: Since no known exploit payload C2 patterns are published, a rule matching outbound HTTP responses containing DLL content to a client that is the IDExpert agent is the only generic approach. Signature-less detection is preferable (see Elastic/SPL below).

Elastic Detection

sequence by host.name, process.executable
  [network where process.name == "IDExpertLogonAgent.exe" and direction == "egress" and destination.port == 80 or destination.port == 443]
  [file where process.name == "IDExpertLogonAgent.exe" and file.extension == "dll" and event.action == "create"]
  [process where process.name == "rundll32.exe" or (process.parent.name == "IDExpertLogonAgent.exe")]

Splunk SPL Query

index=windows earliest=-24h
  (source="WinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode=1)
  OR (source="WinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode=11)
| eval process_conn = if(EventCode==1, Image, "")
| eval dll_create = if(EventCode==11, Image, TargetFilename)
| where Image LIKE "%IDExpert%" OR TargetFilename LIKE "%.dll"
| table _time, host, Image, TargetFilename, CommandLine, DestinationIp, DestinationPort
| sort -_time

Wazuh OSSEC Rule

<group name="sysmon,">
  <rule id="202630" level="12">
    <if_sid>92050</if_sid>  <!-- Sysmon process creation -->
    <field name="win.event.image">\IDExpert</field>
    <description>CVE-2026-3000: IDExpert Logon Agent process execution detected</description>
    <group>cve-2026-3000,dll_download,</group>
  </rule>
  <rule id="202631" level="10">
    <if_sid>202630</if_sid>
    <field name="win.event.originalFileName">\.dll</field>
    <description>CVE-2026-3000: DLL downloaded by IDExpert agent - possible exploitation</description>
    <group>cve-2026-3000,dll_download,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 2/4 — CLAIMED. The vendor (Changing) has stated that a fix exists via their official advisory page (https://www.changingtec.com/news_detail.jsp?item_id=348), but this has not been independently verified, and no patch version or affected version list has been published.

Immediate mitigations (until patch confirmed and applied):

1. Network segmentation: Isolate all hosts running IDExpert Windows Logon Agent from untrusted networks. Restrict inbound and outbound traffic to/from these agents to only known management servers using firewall rules or network ACLs.
2. Monitor network egress: Enable logging of outbound connections from agent processes. Alert on any connection to unexpected IP addresses or unapproved domains.
3. Disable dynamic DLL fetching (if feasible): If the product supports a configuration to pre-stage DLLs locally, disable remote downloads entirely. Check vendor documentation for such an option.
4. Application allowlisting: Deploy application control (e.g., Windows AppLocker or Defender Application Control) that only permits known-signed DLLs to be loaded by the agent process.
5. DNS hardening: If the agent uses DNS to resolve its update/download server, implement DNSSEC and monitor DNS logs for suspicious resolution changes.

Patch / upgrade steps:

1. Contact the vendor (Changing) via their advisory portal to request the patch and confirm whether a newer version is available.
2. Download and apply the patch from https://www.changingtec.com/news_detail.jsp?item_id=348 as directed.
3. After applying, verify the binary version and check that the agent now enforces code-signature validation on any DLL it loads.
4. Test the patched agent in a staging environment before production rollout, focusing on logon functionality and authentication flows.

Long-term hardening:

1. Vendor due diligence: For identity-management products with network-exposed components, demand published security advisories and a documented vulnerability-responsiveness SLA.
2. Code integrity enforcement: Configure Windows to require signed drivers and signed DLLs for all privileged processes; use WDAC (Windows Defender Application Control) policies to restrict which processes can load unsigned code.
3. Credential hygiene: Ensure the agent runs under the least-privilege account feasible, rather than SYSTEM, if product documentation permits.
4. Maintain asset inventory: For products where the vendor does not publish version-affected data, track deployments and review the agent's internal version string to respond faster to future advisories.
5. Monitor vendor advisories: Subscribe to Changing's advisory notifications (https://www.changingtec.com) and re-evaluate this CVE's status as new information becomes available.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-3000 (CVE details, CVSS vector, CWE-494 classification)
2. Vendor Advisory: https://www.changingtec.com/news_detail.jsp?item_id=348 (Patch information — not independently verified)
3. CWE-494 Definition: https://cwe.mitre.org/data/definitions/494.html (Download of Code Without Integrity Check)
4. MITRE ATT&CK — T1190 Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/ (Initial access technique for RCE in exposed services)
5. EPSS Data: https://www.first.org/epss/ (CVE-2026-3000 EPSS score 0.00507)

Threat-actor context: At the time of writing, there are no publicly documented threat-actor campaigns, ransomware group affiliations, or exploit-in-the-wild evidence targeting CVE-2026-3000. The CISA KEV catalogue does not list this CVE (status: NO). However, the PoC status is "Public," indicating that proof-of-concept material exists in the public domain; this elevates the practical risk because the PoC reduces the effort required to build a working exploit. Security teams should treat the vulnerability as actively exploitable even absent public campaign data, given the trivial exploitation requirements (no auth, no user interaction, critical severity).