CVE-2026-79808

Executive Summary

CVE-2026-79808 is a buffer overflow vulnerability in the OnGuard agent component of ClearPass Policy Manager (HPE Aruba Networking). An authenticated local user with low privileges can trigger the overflow to execute arbitrary code with elevated privileges on the affected host, or alternatively disrupt the availability of the OnGuard agent service. With a CVSS v3.1 base score of 7.8 (High), the flaw is locally exploitable, requires low privileges, and needs no user interaction, making it a serious post-authentication privilege escalation and host compromise risk for organizations running ClearPass Policy Manager deployments.

Technical Analysis

ClearPass Policy Manager is a network access control (NAC) platform that provides AAA (authentication, authorization, and accounting), policy enforcement, and endpoint posture assessment. The OnGuard agent is the endpoint-side component that enforces posture policies — it collects device health attributes (OS patch level, antivirus status, disk encryption, etc.) and reports them to the ClearPass Policy Manager server for policy decisions.

The NVD description identifies a buffer overflow vulnerability (no CWE was assigned in the supplied data, but the flaw class maps to CWE-120, Classic Buffer Overflow, or potentially CWE-121/CWE-122 depending on stack vs. heap context). A buffer overflow occurs when a program writes more data to a fixed-length buffer than the buffer can hold, corrupting adjacent memory. Depending on the overflow type:

• Stack-based overflow: overwriting a return address or saved frame pointer can redirect control flow to attacker-controlled code.
• Heap-based overflow: corrupting heap metadata can lead to arbitrary write primitives.

The vulnerability is exploitable by an authenticated local user — meaning the attacker must already have a foothold on the host with valid low-privilege credentials. The CVSS vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H confirms:

• AV:L (Local) — the attack vector is local, not network.
• AC:L (Low) — no special conditions or race windows are required.
• PR:L (Low) — the attacker needs only low-level (non-admin) privileges.
• UI:N (None) — no victim interaction required.
• S:U (Unchanged) — the exploit stays within the same security authority scope (i.e., does not cross a sandbox/virtualization boundary).
• C:H/I:H/A:H — full impact on confidentiality, integrity, and availability.

The "authenticated local user" framing suggests the overflow is reachable through an interface (IPC, local service, or command handler) accessible to a non-privileged local account — for example, a local API, named pipe, or setuid/privileged helper process that the OnGuard agent exposes. Because the description does not specify the exact function, parameter, or input vector, the precise overflow trigger (which input field, which IPC message) cannot be determined from available data and should not be assumed.

The "elevated privileges" impact indicates the OnGuard agent likely runs as a privileged service (root/SYSTEM) or has a privileged helper, so successful code execution in the agent's context yields privilege escalation over the local user's own permissions.

Exploitation Scenarios

No public PoC or exploit code is available. The following attack chain is inferred strictly from the vulnerability class (buffer overflow) and the stated preconditions (authenticated local user). No specific function names, file paths, or parameters are fabricated.

1. Reconnaissance / precondition establishment: The attacker obtains a foothold on a host running the ClearPass OnGuard agent, with at least a low-privilege local account. They enumerate the local attack surface — running services, IPC mechanisms, or command-line interfaces exposed by the OnGuard agent — to identify the input path that feeds the vulnerable buffer.

2. Triggering the flaw class: The attacker supplies crafted input that exceeds the bounds of a fixed-size buffer within the OnGuard agent's processing logic. Because the CVSS metrics indicate AC:L and UI:N, the input can be delivered programmatically with no special timing or victim action. The attacker iterates to determine the overflow offset (e.g., how many bytes to reach a return address or adjacent structure — this offset is not specified in available data).

3. Payload / execution method: At the vulnerability-class level, a buffer overflow enables overwriting adjacent memory, which — depending on the overflow's location (stack vs. heap) — can redirect execution to a payload. The payload executes in the security context of the OnGuard agent, which per the description grants "elevated privileges." The description does not disclose whether the overflow is stack- or heap-based, so the exact overwrite target (return address, function pointer, vtable, or metadata) is not determinable from available data.

4. Post-exploitation impact: Two outcomes are described: (a) arbitrary code execution with elevated privileges, enabling persistent host compromise, credential theft, lateral movement, or disabling of endpoint security controls; or (b) denial of service — crashing the OnGuard agent, which can disrupt endpoint posture enforcement and, in a NAC context, potentially affect network access decisions for that endpoint.

Impact Assessment

• Confidentiality (C:H): Elevated code execution can read any data accessible to the OnGuard agent, including posture data, credentials, and potentially ClearPass integration secrets.
• Integrity (I:H): Arbitrary code execution allows modification of agent behavior, posture reporting (falsifying device compliance), or system files.
• Availability (A:H): The alternative exploitation path — service disruption — can crash the OnGuard agent, degrading endpoint compliance enforcement.

Blast radius: Each affected host is individually compromised; the flaw is local (AV:L, S:U), so it does not automatically propagate. However, in a NAC deployment, compromising an OnGuard agent endpoint could allow an attacker to manipulate posture assessments (making a non-compliant device appear compliant) or pivot within the managed network. The PR:L requirement means the attacker must already have a local account, limiting opportunistic remote exploitation but elevating the value of this flaw in a post-compromise privilege-escalation chain.

No affected version list was provided, so the exact scope of vulnerable ClearPass Policy Manager / OnGuard agent releases remains undefined.

Detection Guidance

Sigma Rule

title: Potential OnGuard Agent Buffer Overflow Exploitation (CVE-2026-79808)
id: 3b9f2c71-8a4e-4d1f-9c02-6e5a7d1b8f30
status: experimental
description: Detects suspicious process crashes or child process creation from the ClearPass OnGuard agent that may indicate local privilege escalation via buffer overflow.
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-79808
author: Threat Intelligence
date: 2026/01/01
tags:
    - attack.privilege_escalation
    - attack.t1068
    - cve.2026.79808
logsource:
    category: process_creation
    product: windows
detection:
    selection_parent:
        ParentImage|endswith:
            - '\OnGuardAgent.exe'
            - '\OnGuard.exe'
    selection_anomaly:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
            - '\whoami.exe'
            - '\net.exe'
    condition: selection_parent and selection_anomaly
falsepositives:
    - Legitimate agent maintenance or update routines
level: high

Note: The exact OnGuard executable name is not confirmed from available data; adjust ParentImage to match the deployed agent binary. This rule targets the behavioral consequence (privileged child process from agent), not the overflow itself.

YARA Rule

rule CVE_2026_79808_OnGuard_BufferOverflow_Indicator
{
    meta:
        description = "Heuristic detection for exploitation artifacts / crash dumps related to CVE-2026-79808 OnGuard agent buffer overflow"
        author = "Threat Intelligence"
        date = "2026-01-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-79808"
        severity = "high"

    strings:
        $onguard = "OnGuard" ascii wide nocase
        $clearpass = "ClearPass" ascii wide nocase
        $crash1 = "STATUS_STACK_BUFFER_OVERRUN" ascii wide
        $crash2 = "stack buffer overrun" ascii wide nocase
        $guard1 = "__stack_chk_fail" ascii wide
        $guard2 = "Security Cookie" ascii wide nocase

    condition:
        (uint16(0) == 0x5A4D or uint32(0) == 0x464C457F) and
        (1 of ($onguard, $clearpass)) and
        (1 of ($crash1, $crash2, $guard1, $guard2))
}

This rule flags binaries/crash artifacts referencing OnGuard or ClearPass alongside buffer-overrun indicators. Tune file scope to agent binaries and Windows Error Reporting dumps.

Suricata IDS Rule

alert tcp $HOME_NET any -> $HOME_NET any (msg:"CVE-2026-79808 ClearPass OnGuard Agent potential overflow payload transfer"; flow:established,to_server; content:"OnGuard"; nocase; content:"|00 00|"; distance:0; threshold: type limit, track by_src, count 1, seconds 60; classtype:attempted-admin; reference:cve,2026-79808; sid:202679808; rev:1;)

CVE-2026-79808 is a local vulnerability (AV:L); network detection is inherently limited. This rule is a best-effort heuristic for anomalous OnGuard-related traffic and should not be relied upon as a primary detection. Local EDR/host telemetry is the authoritative detection layer.

Elastic Detection

process where process.parent.name : ("OnGuardAgent.exe", "OnGuard.exe") and
  process.name : ("cmd.exe", "powershell.exe", "whoami.exe", "net.exe", "rundll32.exe")

Detects privileged child processes spawned from the OnGuard agent, a possible post-exploitation consequence of successful local privilege escalation. Confirm the actual parent process name in your environment.

Splunk SPL Query

index=endpoint (source="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" OR source="WinEventLog:Security")
| search (EventID=1 AND ParentImage="*OnGuard*" AND (Image="*cmd.exe" OR Image="*powershell.exe" OR Image="*whoami.exe"))
   OR (EventID=1000 AND Message="*OnGuard*" AND Message="*buffer*")
| stats count min(_time) as first_seen max(_time) as last_seen values(Image) as child_procs by host, ParentImage
| where count > 0

Correlates process creation with application crash events (Event ID 1000) referencing OnGuard and buffer errors.

Wazuh OSSEC Rule

<group name="windows,cve-2026-79808,">
  <rule id="100798" level="12">
    <if_sid>61603</if_sid>
    <field name="win.eventdata.parentImage">OnGuard</field>
    <field name="win.eventdata.image">(?i)(cmd\.exe|powershell\.exe|whoami\.exe)</field>
    <description>CVE-2026-79808: Possible OnGuard agent buffer overflow privilege escalation — privileged child process spawned</description>
    <mitre>
      <id>T1068</id>
    </mitre>
  </rule>
</group>

Assumes Sysmon process-creation events are ingested (rule 61603 chain). Adjust rule IDs to your Wazuh deployment.

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). No vendor fix, workaround, or affected-version mapping was available at report time.

1) Immediate mitigations

• Restrict local accounts: Because exploitation requires an authenticated local user (PR:L), minimize the number of low-privilege local accounts on hosts running the OnGuard agent and enforce least privilege.
• Monitor agent integrity: Alert on unexpected child processes, crashes, or restarts of the OnGuard agent service (see Detection Guidance).
• Endpoint hardening: Enable OS-level exploit mitigations — ASLR, DEP, stack cookies, and Control Flow Guard — to raise the difficulty of weaponizing a buffer overflow.
• Segment management traffic: Limit which systems can reach ClearPass Policy Manager and OnGuard endpoints to reduce the value of a compromised agent.

2) Patch / upgrade steps

• Monitor HPE Aruba Networking's security advisory portal for ClearPass Policy Manager / OnGuard agent updates addressing CVE-2026-79808. No patch has been published as of this writing.
• When a fix is released, test in a staging NAC environment and roll out to all OnGuard endpoints; extended agent upgrade processes may leave hosts exposed longer.
• Subscribe to HPE Aruba security bulletins to receive patch notifications promptly.

3) Long-term hardening

• Adopt a regular patching cadence for NAC infrastructure and endpoint agents.
• Deploy EDR with process-lineage and exploit-mitigation telemetry on OnGuard endpoints.
• Conduct periodic privilege audits to reduce the population of local accounts available to a would-be attacker.
• Consider application allowlisting to prevent unauthorized executables from running in the agent's context.

References

• NVD — CVE-2026-79808: https://nvd.nist.gov/vuln/detail/CVE-2026-79808
• HPE Aruba Networking Security Advisories: https://www.arubanetworks.com/support-services/security-bulletins/
• CWE-120 — Classic Buffer Overflow: https://cwe.mitre.org/data/definitions/120.html
• MITRE ATT&CK T1068 — Exploitation for Privilege Escalation: https://attack.mitre.org/techniques/T1068/
• CISA Known Exploited Vulnerabilities Catalog (CVE-2026-79808 not listed as of report date): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Threat actor / exploit-in-the-wild status: No public PoC, exploit code, Nuclei template, or CISA KEV entry exists for CVE-2026-79808 at the time of writing. No known threat actor campaigns have been attributed. EPSS has not yet been scored by FIRST.org. The vulnerability remains unpatched, which increases the likelihood of future exploit development and should be treated as a growing risk.