CVE-2026-18811 Overview
CVE-2026-18811 is a command injection vulnerability affecting H3C NX15 routers running firmware version V100R017. The flaw resides in the Add function of the /api/esps endpoint, where the esps.filter.url argument is passed to a system command without sanitization. Attackers can inject shell metacharacters through this parameter to execute arbitrary operating system commands. The vulnerability is exploitable over the network and requires high privileges, according to the published CVSS 4.0 vector. A public proof-of-concept exploit is available, increasing the likelihood of opportunistic attacks against exposed devices. The weakness is classified under CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component.
Critical Impact
Successful exploitation grants attackers arbitrary command execution on the underlying router operating system, resulting in full compromise of confidentiality, integrity, and availability of the affected device.
Affected Products
- H3C NX15 router
- Firmware version V100R017
- /api/esps Add function handler
Discovery Timeline
- 2026-08-04 - CVE-2026-18811 published to NVD
- 2026-08-05 - Last updated in NVD database
Technical Details for CVE-2026-18811
Vulnerability Analysis
The vulnerability exists in the H3C NX15 web management API. Specifically, the Add function within the /api/esps endpoint accepts a URL filter parameter named esps.filter.url from authenticated requests. The affected code path passes this attacker-controlled string into a system-level command execution routine without proper neutralization of shell metacharacters. As a result, an attacker who supplies crafted input containing characters such as ;, |, or backticks can break out of the intended command context. The injected payload executes with the privileges of the web management process, which typically runs as root on embedded router platforms. Public proof-of-concept material referenced by the advisory demonstrates root-level remote code execution using this vector.
Root Cause
The root cause is missing input validation and improper neutralization of special elements passed to a downstream shell interpreter. The esps.filter.url argument is concatenated directly into a command string rather than being passed as a discrete argument to a safe execution primitive. This classic command injection anti-pattern maps to CWE-74.
Attack Vector
An authenticated attacker with administrative access to the router's HTTP management interface sends a crafted request to the /api/esps Add handler. The malicious payload embeds shell metacharacters within the esps.filter.url field. When the firmware processes the request, the injected commands execute on the device. The attack requires network access to the management interface but no user interaction. Full technical details and a working proof-of-concept are hosted in the referenced GitHub PoC Repository.
No verified exploitation code is reproduced here. Refer to the VulDB CVE Details page for the vendor-tracked technical writeup.
Detection Methods for CVE-2026-18811
Indicators of Compromise
- HTTP POST requests to /api/esps containing shell metacharacters (;, |, &, backticks, $()) in the esps.filter.url parameter.
- Unexpected child processes spawned by the router's HTTP daemon, such as /bin/sh, wget, curl, tftp, or nc.
- Outbound connections from the router to unknown IP addresses shortly after configuration API activity.
- Modifications to /etc/passwd, /etc/rc.local, or startup scripts on the device filesystem.
Detection Strategies
- Inspect web server and management API access logs for /api/esps requests with anomalous esps.filter.url values containing non-URL characters.
- Correlate authentication events with immediate configuration API calls to identify credential abuse followed by exploitation attempts.
- Deploy network-based detection rules that flag command injection patterns targeting H3C management endpoints.
Monitoring Recommendations
- Forward router syslog and management interface logs to a centralized SIEM for retention and correlation.
- Alert on any successful authentication to the H3C management interface originating from outside authorized administrative subnets.
- Monitor for new listening ports or reverse shell connections initiated from router IP addresses.
How to Mitigate CVE-2026-18811
Immediate Actions Required
- Restrict access to the H3C NX15 management interface to trusted administrative networks using firewall or ACL rules.
- Rotate all administrative credentials on affected devices, since the vulnerability requires authenticated access.
- Disable remote WAN-side management if it is not strictly required for operations.
- Audit device configurations and startup scripts for unauthorized modifications indicative of prior exploitation.
Patch Information
As of the NVD publication date (2026-08-04), no vendor advisory or fixed firmware release has been published in the referenced sources. Administrators should monitor the H3C security advisories page for an official patch addressing CVE-2026-18811 and apply firmware updates as soon as they become available.
Workarounds
- Place the router management interface behind a VPN and block direct internet exposure of TCP ports serving /api/esps.
- Enforce strong, unique administrator passwords and enable account lockout policies to reduce credential compromise risk.
- Segment the router's management VLAN from user and guest networks to limit lateral movement following exploitation.
# Example ACL to restrict management access to a trusted subnet
# Adjust interface names and subnet to match your environment
access-list 10 permit 10.10.0.0 0.0.0.255
access-list 10 deny any log
line vty 0 4
access-class 10 in
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
