CVE-2026-76751

Executive Summary

CVE-2026-76751 is a critical missing integrity verification vulnerability in the OnGuard agent component of ClearPass Policy Manager, assigned a CVSS base score of 9.8. The flaw allows an unauthenticated, remote attacker to execute arbitrary code on affected endpoints with the elevated privileges of the OnGuard agent. Organizations running ClearPass Policy Manager with the OnGuard agent deployed on managed endpoints are exposed to full compromise of those endpoints, making this a high-priority remediation item.

Technical Analysis

The vulnerability resides in the OnGuard agent, a posture-assessment and endpoint-compliance component associated with ClearPass Policy Manager. According to the NVD description, the defect is a "missing integrity verification" condition — meaning the agent does not adequately validate the integrity of data or code it processes. Because integrity verification is absent, an attacker can supply content that the agent trusts and acts upon without cryptographic or checksum-based validation.

The attack surface is remote and network-reachable, as reflected by the CVSS vector AV:N (network attack vector), AC:L (low attack complexity), PR:N (no privileges required), and UI:N (no user interaction). The absence of required privileges and user interaction indicates that the flaw can be triggered without authenticated access to the agent or an interactive victim. The scope is unchanged (S:U), and the confidentiality, integrity, and availability impacts are all rated High (C:H/I:H/A:H), consistent with the outcome of arbitrary code execution at the agent's privilege level.

The OnGuard agent typically executes with elevated privileges on the endpoint to perform posture checks and enforcement actions. A missing integrity check therefore has an outsize impact: code or data accepted by the agent inherits its elevated execution context. Because the NVD description does not enumerate specific functions, endpoints, parameters, or file paths involved, the precise code-level trigger cannot be stated with confidence. No public advisory detail beyond the description above is available in the supplied intelligence, and no CVE title was provided by the CNA.

Affected version ranges are not enumerated in the available data, and no OSV package mappings were identified. The CWE mapping is treated as CWE-354 (Improper Validation of Integrity Check Value), which is the class most consistent with a "missing integrity verification" description; the supplied data lists no CWE, so this should be considered an analytical classification rather than an authoritative vendor assignment.

Exploitation Scenarios

No public proof-of-concept, exploit code, or Nuclei template exists for this CVE as of the available intelligence, and the CISA KEV catalog does not list it. The following attack chain is inferred at the vulnerability-class level and does not rely on invented implementation details.

1. Reconnaissance and target identification: An attacker identifies reachable ClearPass Policy Manager deployments and their associated OnGuard agents. Because the vulnerability is network-reachable with no authentication requirement, exposed agent communication paths are the primary discovery target.

2. Triggering the flaw class: The attacker supplies crafted input to the OnGuard agent's trust boundary. Because integrity verification is missing, the agent fails to reject tampered or unauthorized content that a properly validated implementation would refuse.

3. Payload and execution method: Leveraging the absent integrity check, the attacker delivers content the agent processes under its own privileges. At the vulnerability-class level, this is an integrity-bypass-to-code-execution chain: the missing check converts attacker-controlled content into trusted execution. No specific function names, endpoints, or parameters can be asserted because none are present in the provided description.

4. Post-exploitation impact: Successful exploitation yields arbitrary code execution on the affected endpoint with the elevated privileges of the OnGuard agent. This could enable persistence, credential access, lateral movement within the managed estate, and disabling of posture or compliance enforcement.

It is important to note that the attack chain above is inferred from the vulnerability class; no public PoC is available, and no exploit-in-the-wild evidence is present in the supplied data.

Impact Assessment

With a CVSS base score of 9.8, CVE-2026-76751 is rated Critical. The vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H indicates a remotely exploitable, low-complexity flaw requiring no privileges or user interaction, with high confidentiality, integrity, and availability impact. The blast radius centers on endpoints running the OnGuard agent. Because the agent operates with elevated privileges, a single compromised endpoint can be fully controlled by an attacker. In enterprise environments where OnGuard is broadly deployed for network access control and posture assessment, the aggregate exposure across many managed endpoints is significant. Business impact includes potential loss of endpoint integrity, bypass of compliance controls, exposure of sensitive data on managed systems, and disruption of network access enforcement workflows.

Detection Guidance

Sigma Rule

title: Suspicious OnGuard Agent Child Process Execution
id: 8f2a1c44-7b9e-4d21-9a3c-0d5e6f7a8b90
status: experimental
description: Detects potential abuse of ClearPass OnGuard agent leading to arbitrary code execution under elevated agent privileges.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-76751
author: valtersit.com
date: 2026-01-01
logsource:
  category: process_creation
  product: windows
detection:
  selection_parent:
    ParentImage|endswith:
      - '\OnGuardAgent.exe'
      - '\OnGuard.exe'
  selection_suspicious:
    Image|endswith:
      - '\cmd.exe'
      - '\powershell.exe'
      - '\wscript.exe'
      - '\cscript.exe'
      - '\rundll32.exe'
  condition: selection_parent and selection_suspicious
falsepositives:
  - Legitimate administrative scripts invoked by the agent
level: high

YARA Rule

rule CVE_2026_76751_OnGuard_Integrity_Bypass
{
    meta:
        description = "Detects tampered content potentially delivered to ClearPass OnGuard agent exploiting missing integrity verification (CVE-2026-76751)"
        author = "valtersit.com"
        date = "2026-01-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-76751"
        severity = "critical"
    strings:
        $a = "OnGuard" ascii nocase
        $b = "ClearPass" ascii nocase
        $c = "posture" ascii nocase
        $d = { 4D 5A }
    condition:
        $d at 0 and any of ($a, $b, $c)
}

Suricata IDS Rule

alert tcp any any -> any any (msg:"CVE-2026-76751 Possible ClearPass OnGuard Agent Integrity Bypass Attempt"; flow:to_server,established; content:"OnGuard"; nocase; content:"ClearPass"; nocase; threshold:type both, track by_src, count 5, seconds 60; classtype:attempted-admin; sid:202676751; rev:1;)

Elastic Detection

process where event.type == "start" and
  process.parent.name in ("OnGuardAgent.exe", "OnGuard.exe") and
  process.name in ("cmd.exe", "powershell.exe", "wscript.exe", "cscript.exe", "rundll32.exe")

Splunk SPL Query

index=endpoint sourcetype=WinEventLog:Security EventCode=4688
| where match(ParentProcessName, "(?i)OnGuard")
| where match(NewProcessName, "(?i)(cmd|powershell|wscript|cscript|rundll32)\.exe")
| stats count by host, ParentProcessName, NewProcessName, Account_Name
| sort - count

Wazuh OSSEC Rule

<group name="clearpass_onguard,">
  <rule id="100751" level="12">
    <if_sid>60009</if_sid>
    <field name="win.eventdata.parentImage">OnGuard.*\.exe</field>
    <field name="win.eventdata.image">cmd\.exe|powershell\.exe|wscript\.exe|rundll32\.exe</field>
    <description>CVE-2026-76751: Suspicious child process spawned by ClearPass OnGuard agent - possible integrity bypass exploitation.</description>
    <mitre>
      <id>T1190</id>
      <id>T1059</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence is 0/4 — the vulnerability is UNPATCHED, with no patch evidence from any tracked source.

1. Immediate mitigations: Restrict network reachability to OnGuard agent communication paths, enforcing least-privilege network segmentation so only known ClearPass Policy Manager infrastructure can reach the agents. Monitor for anomalous child processes spawned by the agent, and apply application allowlisting on endpoints to prevent unauthorized code execution under agent privileges. Where feasible, reduce agent privilege levels to the minimum required for posture checks.

2. Patch/upgrade steps: No vendor patch reference is available as of this report. Contact Aruba/HPE support for ClearPass Policy Manager to determine whether a fixed OnGuard agent build is available, and subscribe to vendor security advisories for CVE-2026-76751. Do not assume version ranges — obtain authoritative affected-version data directly from the vendor.

3. Long-term hardening: Enforce integrity verification for all agent-processed content as a design requirement, implement mutual TLS and cryptographic signing for agent communications, and adopt continuous monitoring for posture-agent abuse. Routinely review agent privilege scope and apply defense-in-depth controls across the endpoint estate.

References

• NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2026-76751
• HPE Aruba Networking security advisories: https://www.arubanetworks.com/support-services/security-bulletins/
• CISA Known Exploited Vulnerabilities catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CVE-2026-76751 not listed as of this report)
• FIRST EPSS: https://www.first.org/epss (CVE-2026-76751 not yet scored)
• MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/

No public proof-of-concept, exploit code, Nuclei template, or evidence of active exploitation/threat-actor campaigns was identified in the available data.