CVE-2026-73809

Executive Summary

CVE-2026-73809 describes a cleartext transmission of sensitive information vulnerability (CWE-319) affecting certain Ebyte gateway products. The web management interface fails to adequately protect communications using transport-layer encryption, allowing a network-adjacent attacker to intercept authentication or session-related data between a user and the device. With a CVSS base score of 7.5 (High), successful exploitation results in disclosure of sensitive information and potential unauthorized access to device management functionality. As of this report, no patch is available from any tracked source, and the vulnerability remains unaddressed by the vendor.

Technical Analysis

Vulnerability Class: Cleartext Transmission of Sensitive Information (CWE-319)

The vulnerability stems from the absence or misconfiguration of transport-layer encryption (e.g., TLS/HTTPS) on the web management interface of affected Ebyte gateway devices. When a user authenticates to the device's management interface, sensitive data — including credentials, session cookies, or session tokens — is transmitted in plaintext over the network.

Attack Surface: The attack surface is the network path between an authenticated or authenticating user and the Ebyte gateway's web management interface. Because the vulnerability is network-based (AV:N) with Low attack complexity (AC:L) and No privileges required (PR:N), any attacker capable of passively observing network traffic — through ARP spoofing, rogue access point deployment, switch port mirroring, or other network sniffing techniques — can exploit this flaw.

Mechanism: The web management interface either does not implement TLS at all or allows fallback to unencrypted HTTP. When a user accesses the management page and submits credentials or receives a session token, the data traverses the network in cleartext. An attacker with access to the network traffic (via packet capture tools or network tapping) can reconstruct the authentication exchange and extract valid credentials or session identifiers.

Code-level detail: Insufficient technical detail is available in the public description to identify specific HTTP endpoints, form fields, or protocol behaviors. The description does not disclose device model numbers, firmware versions, or exact interface paths. The vulnerability is described at a class level, and no vendor advisory with implementation specifics has been published.

Exploitability notes: No public PoC, Nuclei template, or exploit code has been identified. The flaw is inherently passive — exploitation requires no direct interaction with the target beyond placing the attacker in a position to monitor traffic.

Exploitation Scenarios

No public PoC is available; the following attack chain is inferred from the vulnerability class and the NVD description.

Step 1 — Reconnaissance / Target Identification: The attacker identifies Ebyte gateway devices on the network. This can be accomplished through network scanning to identify devices listening on standard web management ports (e.g., TCP 80 if HTTP-only, or TCP 443 if a misconfigured TLS implementation is present). Services banners or default web interface titles may identify the device as an Ebyte gateway. On wireless networks, the attacker may first compromise, or already control, a rogue access point to funnel traffic.

Step 2 — Triggering the Flaw: The attacker does not actively trigger the flaw. Instead, the attacker positions a packet capture tool on the communication path between a legitimate user (administrator) and the gateway's web management interface. This can be achieved via ARP spoofing on a local LAN segment, passive monitoring on a shared medium (e.g., wired hub or unencrypted Wi-Fi), or a malicious network tap. When the administrator navigates to the management interface and submits credentials, the traffic transits the network in cleartext.

Step 3 — Payload / Execution Method: At the vulnerability-class level, no payload is sent by the attacker. Instead, the attacker captures the cleartext transmission using a network sniffer. The captured data contains authentication material (username/password pair in the HTTP request body or headers) and/or session tokens (e.g., cookies) returned by the gateway. Tools such as Wireshark or tcpdump will reveal these materials when filtering on HTTP traffic to the device's IP address.

Step 4 — Post-Exploitation Impact: With the harvested credentials or session token, the attacker gains the ability to impersonate the legitimate administrator. This permits full control of the device management functionality, including but not limited to changing configuration, reading sensitive parameters (e.g., network keys, connected device credentials), enabling/disabling features, and potentially using the gateway as a pivot point into the broader network. Session hijacking could also be performed in real time if the attacker continuously monitors traffic.

Impact Assessment

CVSS Analysis: The base score of 7.5 (High) reflects a network-exploitable (AV:N) vulnerability with low attack complexity (AC:L), no required privileges (PR:N), and no user interaction (UI:N). The scope is unchanged (U:), with high confidentiality impact (C:H) — authentication material and session data are exposed — and no integrity (I:N) or availability (A:N) impact. The confidentiality-only impact limits the score to 7.5 rather than a higher critical rating.

Business Impact:

• Credential disclosure: Administrative credentials for the gateway are exposed to any capable network sniffer. This could cascade to reuse of the same credentials on other organizational systems if administrators use password reuse.
• Unauthorized device access: An attacker with stolen credentials or session tokens gains full access to the device's management interface, enabling configuration tampering and data exfiltration.
• Network infiltration: Compromised gateways may act as entry points into deeper network segments, enabling lateral movement.
• Compliance violations: Sensitive data exposure through cleartext transmission may violate regulatory frameworks (e.g., GDPR, PCI DSS, HIPAA) depending on the data traversing the network.

Affected Systems: The NVD description identifies "certain Ebyte gateway products" without disclosing specific model numbers. Ebyte (Chengdu Ebyte Electronic Technology Co., Ltd.) produces a range of wireless gateways for LoRa, Zigbee, Wi-Fi, and other protocols commonly used in IoT deployments. The exact affected product line and firmware versions are unknown at the time of writing.

Blast Radius: The immediate blast radius is limited to the local network segment where the gateway resides, since the attacker must observe traffic. However, cascading impacts (credential reuse, configuration sabotage, lateral movement) can extend the blast radius across the entire organization.

Detection Guidance

Sigma Rule

title: Cleartext HTTP Authentication to Ebyte Gateway
id: 3f8b1d6e-2a9c-4e5f-8b0d-1c2a3b4e5f6a
status: experimental
description: Detects cleartext HTTP authentication attempts to Ebyte gateway management interfaces, indicative of CVE-2026-73809 exploitation.
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-73809
author: Valtersit Threat Intelligence
date: 2026/01/01
logsource:
    category: webserver
    product: generic
detection:
    selection_http:
        cs-method: 'POST'
        cs-uri-query|contains:
            - 'login'
            - 'auth'
            - 'session'
        sc-status: 200
    selection_plaintext:
        cs-uri-scheme: 'http'
    condition: selection_http and selection_plaintext
falsepositives:
    - Legitimate misconfigured devices used in lab environments
    - Older devices with no TLS support
level: medium

YARA Rule

rule Detect_Ebyte_Gateway_Cleartext_Auth {
    meta:
        author = "Valtersit Threat Intelligence"
        description = "Detects traffic patterns indicative of cleartext authentication to Ebyte gateway web interfaces (CVE-2026-73809)"
        cve = "CVE-2026-73809"
        date = "2026-01-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-73809"
    strings:
        $http_auth = "POST /" ascii
        $content_type = "application/x-www-form-urlencoded" ascii
        $password_field = "password=" ascii
        $user_field = "user=" ascii
        $gateway_marker1 = "Ebyte" ascii wide
        $gateway_marker2 = "ebyte" ascii wide
        $session_cookie = "Set-Cookie: session" ascii
    condition:
        uint16(0) == 0x3a48 and  // "H:" check for HTTP header start (simplified)
        $http_auth and $content_type and $password_field and $user_field and
        (1 of ($gateway_marker*) or #http_auth > 2)
}

Suricata IDS Rule

alert http any any -> $HOME_NET any (msg:"CVE-2026-73809 - Cleartext Authentication to Ebyte Gateway"; flow:to_server,established; http.method; content:"POST"; http.uri; content:"/"; http.uri.raw; content:"login"; sid:7000001; rev:1; metadata:created_at 2026_01_01, updated_at 2026_01_01; reference:url, https://nvd.nist.gov/vuln/detail/CVE-2026-73809; classtype:attempted-admin;)

Note: This rule detects POST requests containing "login" in the URI on clear HTTP (non-TLS) ports. Additional filtering on port 80 and assessment of session/cookie traffic (HTTP-level, unencrypted) can refine detection. Because no specific URI is publicly known, the rule relies on generic login patterns — tune the URI keywords based on observed legitimate traffic.

Elastic Detection

network where event.category == "network" and network.protocol == "http"
    and http.request.method == "POST"
    and destination.port == 80
    and http.request.body.content like~ "*password*"
    and http.response.status_code == 200
    and (source.address == "10.0.0.0/8" or source.address == "172.16.0.0/12" or source.address == "192.168.0.0/16")

Alternative: Use the URI-based approach:

network where event.category == "network"
    and network.protocol == "http"
    and destination.port == 80
    and http.request.uri like~ "*login*"

Splunk SPL Query

index=proxy OR index=web OR index=network
| where protocol = "http"
| search method="POST" dest_port=80
| regex _raw "(?i)(password|passwd|pwd|user|username)="
| search uri=*login* OR uri=*auth*
| table _time, src_ip, dest_ip, dest_port, method, uri, http_user_agent
| sort - _time
| eval alert = "CVE-2026-73809: Cleartext auth attempt to Ebyte gateway"

Wazuh OSSEC Rule

<group name="cve-2026-73809,">
  <rule id="100738" level="10">
    <decoded_as>web</decoded_as>
    <field name="method">^POST$</field>
    <field name="uri" type="pcre2">(?i)(login|auth)</field>
    <field name="protocol">HTTP</field>
    <description>CVE-2026-73809: Cleartext authentication attempt detected against web management interface</description>
    <group>access_control,web_application_attack,</group>
  </rule>
</group>

Note: The rule ID (100738) is a suggested non-conflicting ID; adjust to an unused ID range within your Wazuh deployment.

Mitigation & Patch Guidance

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

1) Immediate Mitigations

• Network segmentation: Isolate Ebyte gateway management interfaces on a dedicated VLAN with restricted access. Do not expose management interfaces to the internet or untrusted network segments.
• VPN enforcement: Require that administrators access the management interface only via a VPN or an encrypted jump host, ensuring the network path between the user and the device is encrypted even if the device itself is not.
• Network monitoring: Enable passive network monitoring on management segments to detect cleartext HTTP traffic to gateway IP addresses. Alert on any HTTP (port 80) traffic to these devices.
• Disable remote management: If remote management is not required, disable it entirely at the device or firewall level.

2) Patch / Upgrade Steps

• Monitor vendor channels: Track Ebyte's official advisory page and firmware release notes (ebyte.com). No patch source has been identified as of this report.
• Contact vendor support: Open a ticket with Ebyte support referencing CVE-2026-73809 to request remediation timelines.
• Version tracking: Regularly check for firmware updates for the specific gateway model in use. Do not install untested third-party firmware.

3) Long-Term Hardening

• Encryption at the network layer: Deploy IPsec or WireGuard tunnels for all management communication paths to enforce encryption regardless of application-layer behavior.
• Credential hygiene: Enforce unique, high-entropy passwords for all gateway accounts; forbid password reuse across administrative accounts.
• Monitoring and logging: Enable syslog or SNMP trap forwarding to a central SIEM to monitor authentication activity on the gateway.
• Procurement policy: Require that all future gateway purchases mandate native TLS 1.2+ support for management interfaces as a procurement condition.
• Periodic reassessment: If a patch remains unavailable, periodically reassess risk and consider replacing affected devices with alternatives that support encrypted management interfaces.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-73809 — Official NVD record with CVSS vector and description.
2. CWE-319 Reference: https://cwe.mitre.org/data/definitions/319.html — Common Weakness Enumeration definition for cleartext transmission of sensitive information.
3. Ebyte Official Website: https://www.ebyte.com — Vendor product page and firmware download location (patch tracking).
4. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog — No KEV entry exists for this CVE; check periodically for updates.
5. FIRST EPSS: https://www.first.org/epss/ — EPSS score not yet assigned; monitor for future scoring.

Threat Actor Campaigns / Exploit-in-the-Wild Evidence: No known threat actor campaigns or in-the-wild exploitation activity has been publicly documented for this CVE. The vulnerability remains unpatched with no available exploit artifacts; however, the passive nature of the flaw (traffic sniffing) means exploitation may go undetected without active network monitoring. Continuous surveillance of dark web forums and exploit repositories is recommended.