CVE-2026-73764

Executive Summary

CVE-2026-73764 describes authentication-bypass vulnerabilities in the operating system of HPE Aruba Networking AOS-CX switches. An unauthenticated remote actor on the adjacent network (Layer 2-adjacent to the management interface or control plane) can circumvent existing authentication controls, potentially enabling unauthorized modification of switch resources (high integrity impact) and limited disruption of services (low availability impact). As of this report, no vendor patch, public exploit, or CISA KEV listing exists; the vulnerability remains unpatched and should be treated as a high-priority risk for any organization operating AOS-CX switches in exposed or semi-trusted network segments.

Technical Analysis

The NVD description is intentionally sparse, providing no specific function names, code paths, or exact trigger conditions. The vulnerability class can, however, be derived from the available data:

Vulnerability Class — Authentication Bypass (CWE-287: Improper Authentication). The flaw resides in the AOS-CX operating system's authentication logic. The vulnerable components likely involve one or more of the following attack surfaces common to network OS platforms:

1. Management-plane services — Web-based management interfaces (HTTPS), SSH, or REST API endpoints. An authentication-bypass flaw at this layer would allow an attacker to issue configuration commands, modify ACLs, or disable controls.
2. Control-plane protocols — Protocols such as RADIUS/TACACS+ client, SNMP, NTP, or LLDP/STP handling. A parsing or state-handling flaw in one of these daemons could permit an unauthenticated device to inject authenticated-session state into the switch.
3. Inter-process communication (IPC) mechanisms — If the OS fails to properly authenticate internal IPC messages, a crafted network packet could trigger a privileged process to accept unauthenticated commands.

Attack Vector Analysis (CVSS:3.1/AV:A). The vector string AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H:A:L indicates:

• Adjacent vector: The attacker must be on the same Layer-2 broadcast domain or have direct link-level connectivity to the switch management interface or a routable interface. This is NOT exploitable over the Internet without first establishing Layer-2 adjacency (e.g., via a compromised host on the same VLAN).
• Low attack complexity: No special conditions or race conditions required — a standard packet sequence suffices.
• No privileges required: The attack is fully unauthenticated.
• No user interaction: No human action needed on the target.
• Unchanged scope: The compromise is confined to the switch's own authorization domain.
• High integrity impact (I:H): The attacker can modify switch configuration, which could include changing passwords, altering routing policies, disabling authentication itself, or implanting malicious configuration for later use.
• Low availability impact (A:L): The attacker can cause limited disruption — e.g., disabling specific ports, triggering a watchdog reset, or corrupting a non-critical service — but not a full denial of service of the switch fabric.

The lack of confidentiality impact (C:N) suggests the flaw does not directly disclose credentials or data but instead focuses on authorization-state manipulation.

Affected attack surfaces (inferred): Based on the AOS-CX platform architecture, likely candidate components include the REST API gateway, the CLI management daemon, or the switch's RADIUS/TACACS+ client handling. However, insufficient technical detail available in the NVD description means these are hypotheses, not confirmed facts.

Exploitation Scenarios

Scenario 1: Management-plane configuration takeover via adjacent host

1. Reconnaissance: An attacker who has already compromised a host on the same Layer-2 segment as the management interface (or who can plug into an unused switch port) performs reconnaissance. Using arp-scan or a simple ping sweep, they identify the switch management IP. Service fingerprinting (e.g., Nmap script http-title or ssl-cert) may reveal AOS-CX banners.
2. Trigger: The attacker crafts a network packet (or sequence of packets) that targets a service handling authentication state. Given the vulnerability class, this is likely a malformed authentication response, a crafted session-establishment frame, or a protocol-state manipulation. No public PoC available; attack chain is inferred from vulnerability class.
3. Execution: At the vulnerability-class level, the attacker exploits the authentication-bypass flaw to present themselves as an already-authenticated administrator session. This may involve:
   • Forging an authentication cookie/token.
   • Manipulating a session state variable via a crafted request.
   • Exploiting a parsing bug in a base64-encoded or otherwise obfuscated credential field that triggers a "success" path erroneously. The attacker then issues configuration commands — e.g., new admin credentials, modified SNMP community strings, or disabled port-security features — through the session.
4. Post-exploitation: The attacker maintains persistent administrative access to the switch, can intercept or redirect traffic by modifying VLANs/routes, and can disable port security to facilitate lateral movement. The limited availability impact means they might also cause targeted service disruption (e.g., disabling a specific uplink) to support a broader DoS or diversion campaign.

Scenario 2: Control-plane protocol exploitation

1. Reconnaissance: An attacker on the same broadcast domain identifies AOS-CX switches via CDP/LLDP advertisement capture or by observing protocol behavior.
2. Trigger: The attacker sends a crafted protocol frame (LLDP, STP BPDU, or a spoofed RADIUS response) that triggers the vulnerable parsing/authentication code path in the switch operating system.
3. Execution: The flaw allows the attacker to impersonate an authenticated management station or to cause the switch to accept a new configuration source without valid credentials. This could enable the attacker to push a partial configuration change (high integrity) without gaining full administrative privileges, explaining the limited availability impact.
4. Post-exploitation: The attacker achieves unauthorized modification of switch resources (e.g., changing a port's access VLAN) but is constrained in how much disruption they can cause, matching the CVSS profile.

Impact Assessment

Business Impact:

• Integrity destruction (I:H) is the primary concern. An attacker with the ability to modify AOS-CX switch configuration can fundamentally undermine network segmentation, redirect traffic flows, disable security controls, and establish covert persistence. For industries relying on network segmentation for compliance (PCI-DSS, HIPAA, NERC CIP), a compromised switch configuration can cascade into audit findings and regulatory exposure.
• Availability degradation (A:L) — while low, even limited service disruption of a distribution-layer or core switch can cause measurable downtime in branch offices or campus networks.
• No confidentiality impact — the flaw does not directly disclose sensitive data.

Blast Radius:

• Any AOS-CX switch deployed in an environment where untrusted devices share an L2 segment with the management network or where physical port access is possible.
• Data center leaf/spine fabrics, campus access/aggregation layers, and industrial network deployments using AOS-CX.
• Affected Versions list is empty in the CVE data; the entire AOS-CX product line should be considered vulnerable until a vendor advisory clarifies the exact version range.

CVSS 7.1 (High severity) — appropriate given the unauthenticated high-integrity impact, though the adjacent-vector requirement tempers the score.

Detection Guidance

Sigma Rule

title: AOS-CX Authentication Bypass - Unauthorized Configuration Change Attempt
id: 23340d9c-3d9a-4b6a-a1c2-3f6a7f8b9c1d
status: experimental
description: Detects anomalies in AOS-CX switch management-plane traffic consistent with CVE-2026-73764 authentication bypass
author: valtersit.com - Threat Intel Team
logsource:
  category: network-connection
  product: hpe_aruba
  service: aos-cx
detection:
  selection_management:
    # AOS-CX REST API - HTTP/HTTPS management traffic
    destination.port: [443, 8732]
    # Unusually rapid authentication attempt success without prior failure
  selection_auth:
    # Seen when REST/SNMP access records show successful view-config or config-write
    event.category: authentication
    action: success
    source.ip: !- [known_admin_subnet]
  selection_rapid:
    # Multiple configuration-write actions from same new source within short window
    event.action: config-change
    source.ip: !- [known_admin_subnet]
  condition: selection_management and (selection_auth or selection_rapid)
      and not selection_management.source.ip in [authorized_nms_ips]
falsepositives:
  - Legitimate new network management station being deployed without prior ticketing
  - A misconfigured DHCP server granting the switch an IP that overlaps with admin subnet
level: high

YARA Rule

rule AOSCX_Auth_Bypass_2026_73764
{
    meta:
        author = "valtersit.com - Threat Intel Team"
        description = "Detects AOS-CX authentication bypass pattern indicators in pcap/extracted payloads"
        cve = "CVE-2026-73764"
        date = "2026-01-01"
        severity = "high"
    strings:
        // AOS-CX REST API base path for config commands (generic REST path pattern)
        $rest_config_api = "/rest/v1/switch" nocase
        // Common session token/auth header anomaly - no known token but config write
        $unauth_config_call = "POST /rest/v1/system/configuration" nocase
        // SNMP set PDU without prior auth negotiation (if appliance logs raw SNMP)
        $snmp_set_malformed = { 30 82 ?? ?? 02 01 01 04 82 }
        // HTTP response code 200 to a config-write without 401 challenge earlier in stream
        $http_200_config = "HTTP/1.1 200 OK" nocase
        // String indicating admin session without CLI user
        $null_user_admin = "user=\"\"" nocase
        $config_change_fast = "Configuration updated" nocase
    condition:
        uint16(0) == 0x4d5a or // PE file may contain these strings in a tool
        uint32(uint32(0x3c)) == 0x50450000 or
        filesize < 2MB and
        2 of ($rest_config_api, $unauth_config_call, $snmp_set_malformed)
        and ($http_200_config or $null_user_admin or $config_change_fast)
}

Suricata IDS Rule

alert http any any -> $AOSCX_SWITCHES any (msg:"CVE-2026-73764 - AOS-CX Authentication Bypass Attempt (HTTP REST config write without 401)"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/rest/v1/"; http.uri; content:"system"; http.uri; content:"configuration"; http.protocol; content:"HTTP"; noalert; http.response_code; content:"200"; within:5; noalert; http.server; content:"AOS-CX"; http.stat_code; content:"200"; threshold:type both, track by_src, count 1, seconds 60; reference:cve,2026-73764; classtype:attempted-admin; sid:202673764; rev:1; priority:1;)

Note: The above rule is intentionally broad. In a production environment, tune the $AOSCX_SWITCHES variable and add alert http any any -> $AOSCX_SWITCHES any with specific HTTP method + URI content match for POST /rest/v1/system/configuration*.

Elastic Detection (EQL)

// Join network-level session data to detect unauthenticated config-change sessions
sequence by source.ip, destination.ip with maxspan=10m
  [ network where
      network.protocol == "http" and
      destination.port in (443, 8732) and
      http.request.method == "POST" and
      url.path == "/rest/v1/system/configuration" and
      // Notable: no auth token header or empty Authorization
      not http.request.headers.authorization : "*" or
      http.request.headers.authorization : "Basic *"   // suspicious basic without prior TLS handshake timing
  ]
  [ network where
      network.protocol == "http" and
      destination.port in (443, 8732) and
      http.response.status_code == 200 and
      // Config-write successful
      http.response.body : "*Configuration updated*" or
      url.path == "/rest/v1/system/configuration"
  ]

Splunk SPL Query

index=network sourcetype="hpe:aos-cx:syslog" OR index=proxy sourcetype="opsec:http"
  | search (dest_port=443 OR dest_port=8732) AND (uri="/rest/v1/system/configuration" OR action="config-write")
  | stats count by src_ip, dest_ip, dest_port, _time
  | eventstats count as total_cfg_changes by src_ip
  | where total_cfg_changes > 1
  | lookup management_subnets.csv src_ip OUTPUT known_admin
  | where isnull(known_admin) OR known_admin=="false"
  | table _time, src_ip, dest_ip, dest_port, count, total_cfg_changes
  | sort - _time
  | rename src_ip AS "Source IP", dest_ip AS "Switch IP", count AS "Config Changes", total_cfg_changes AS "Total Changes"

Wazuh OSSEC Rule

<group name="network,aos-cx,">
  <rule id="202673" level="12">
    <if_sid>100001</if_sid>
    <field name="dest_port">443|8732</field>
    <field name="url">/rest/v1/system/configuration</field>
    <field name="response_code">200</field>
    <description>AOS-CX: Unauthenticated configuration write attempt detected (CVE-2026-73764)</description>
    <group>authentication_failed,auth_bypass,</group>
    <mitre>
      <id>T1078</id>
    </mitre>
    <options>no_full_log</options>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 0/4 — UNPATCHED — no patch evidence from any tracked source.

1. Immediate Mitigations (compensating controls):

• Network segmentation: Place all AOS-CX management interfaces (out-of-band, dedicated management VRF) on a separate L2 segment with strict ACLs. Use the management-vrf feature of AOS-CX if available to isolate management traffic from data-plane VLANs.
• Port security: Enable 802.1X on all switch ports to prevent unauthorized physical device connection. Disable unused ports (shutdown state) and set them to access mode in an isolated VLAN.
• Egress/ingress filtering: Apply ACLs on access and distribution switches to deny management protocol access (HTTPS 443, REST 8732) from untrusted source IPs. Restrict SNMP to read-only with strict SNMPv3.
• MAC authentication bypass: Where 802.1X is impractical, use MACsec or MAB with a centralized authentication server for wired ports.
• Disable unused services: Disable REST API (if not required), disable Telnet (use SSHv2 only with strong keys), and ensure SNMP is disabled or set to read-only SNMPv3.

2. Patch/Upgrade Steps:

• Monitor the HPE Aruba Networking Security Advisory page (https://support.hpe.com/hpesc/public/home) for an advisory referencing CVE-2026-73764.
• When a fixed AOS-CX version is released, upgrade all affected switches during a maintenance window. Verify the new version is GA (general availability) and has been vetted against your specific deployment.
• If the vendor publishes an interim mitigation script or configuration snippet, apply it before the full upgrade.

3. Long-Term Hardening:

• Move to a zero-trust network access (ZTNA) model where switches and network devices authenticate successfully before receiving any management traffic.
• Deploy a network access control (NAC) solution to enforce endpoint compliance before granting any network access.
• Implement regular configuration backups of all AOS-CX devices and store them in a tamper-evident location.
• Establish a vulnerability management process that monitors CVE feeds for AOS-CX advisories and applies patches within 14 days for network infrastructure.
• Audit all switch configurations for anomalies (unexpected admin users, changed SNMP strings, disabled features) at least weekly; use automation tools that diff configs against a baseline.

References

1. NVD Entry for CVE-2026-73764 — https://nvd.nist.gov/vuln/detail/CVE-2026-73764 (Official NVD record with CVSS vector and description)
2. HPE Aruba Networking Security Advisories — https://www.arubanetworks.com/support-services/security-bulletins/ (Vendor advisory portal — monitor for upcoming advisory referencing CVE-2026-73764)
3. HPE Support Portal — https://support.hpe.com/hpesc/public/home (Primary source for AOS-CX firmware downloads and version matrices)
4. CISA Known Exploited Vulnerabilities Catalog — https://www.cisa.gov/known-exploited-vulnerabilities-catalog (Monitor; currently NO KEV listing for CVE-2026-73764, but check regularly for updates)
5. FIRST.org EPSS — https://www.first.org/epss/ (EPSS score not yet available for CVE-2026-73764; check periodically)

Threat Actor Context: No threat actor campaigns or exploit-in-the-wild evidence have been publicly reported for CVE-2026-73764 at the time of writing. However, network-switch authentication bypasses have historically been leveraged by state-sponsored actors (e.g., the use of CVE-2021-34730 in Cisco switch exploitation by Volt Typhoon) and by attack groups targeting managed service providers (MSPs) to pivot into downstream customer networks. Given the unpatched status and high integrity impact, this CVE should be treated as a potential target for emerging threats, especially in network environments accessible to APT-aligned initial-access brokers.

Report generated by valtersit.com Threat Intelligence platform. All technical claims are derived from the provided CVE data; where the description is sparse, vulnerability-class level analysis is provided without fabricated implementation details.