CVE-2026-18900 Overview
CVE-2026-18900 is an operating system command injection vulnerability affecting H3C NX15 V100R017 routers. The flaw resides in the file.exec function exposed through the /api/esps endpoint of the Backend RPC component. Attackers can manipulate the File argument to inject arbitrary operating system commands executed by the device. The issue is classified under CWE-77, Improper Neutralization of Special Elements used in a Command. Remote exploitation is possible over the network after authentication, and a public proof-of-concept exploit has been released.
Critical Impact
Authenticated remote attackers can achieve root-level command execution on affected H3C NX15 devices through the /api/esps endpoint, compromising the confidentiality, integrity, and availability of the router and connected network segments.
Affected Products
- H3C NX15 firmware version V100R017
- H3C NX15 Backend RPC component exposing the /api/esps endpoint
- Deployments where the file.exec function is reachable by authenticated users
Discovery Timeline
- 2026-08-05 - CVE-2026-18900 published to NVD
- 2026-08-05 - Last updated in NVD database
Technical Details for CVE-2026-18900
Vulnerability Analysis
The vulnerability exists in the Backend RPC handler that serves the /api/esps endpoint on the H3C NX15 router. The file.exec function accepts a File parameter from client requests and passes it to an operating system command interpreter without adequate sanitization. Attackers who supply shell metacharacters or command separators within the File argument cause the router to execute injected commands in the context of the RPC service, which runs as root according to the public research report.
The EPSS score of 2.384% (82nd percentile) reflects meaningful exploit activity likelihood given the availability of a public GitHub PoC Script. Successful exploitation grants complete control of the device, enabling traffic interception, pivoting into internal networks, and persistent implantation.
Root Cause
The root cause is improper neutralization of special elements in a command string [CWE-77]. The file.exec handler concatenates attacker-controlled input from the File argument into an operating system command without escaping, quoting, or validating shell metacharacters. Any request that reaches the RPC dispatcher with a crafted File value can therefore break out of the intended command and append arbitrary shell payloads.
Attack Vector
Exploitation is performed over the network against the router's management interface. The attacker must first authenticate to the device, then send a crafted request to /api/esps invoking the file.exec RPC method with a malicious File value. The public proof-of-concept demonstrates post-authentication remote code execution as root. See the GitHub Security Report for the request structure and payload construction.
No verified exploit code is reproduced here. Refer to the linked research artifacts for the technical exploitation details.
Detection Methods for CVE-2026-18900
Indicators of Compromise
- HTTP or HTTPS requests to the /api/esps endpoint containing shell metacharacters such as ;, |, `, $(, or && within the File parameter
- Unexpected child processes spawned by the Backend RPC service on the H3C NX15 device
- Outbound connections from the router to unknown infrastructure following administrative logins
- New cron entries, modified startup scripts, or unexpected binaries in writable firmware partitions
Detection Strategies
- Inspect router management traffic for POST requests to /api/esps with anomalous File argument content and alert on shell syntax patterns
- Correlate authenticated administrative sessions with subsequent process creation or network egress from the device
- Baseline expected RPC method usage on the NX15 and flag first-time invocations of file.exec from non-administrative source addresses
Monitoring Recommendations
- Forward router syslog, authentication events, and web-management access logs to a centralized analytics platform for retention and correlation
- Monitor for repeated authentication attempts against the NX15 web interface, since exploitation requires valid credentials
- Track configuration drift and firmware integrity to identify post-exploitation persistence
How to Mitigate CVE-2026-18900
Immediate Actions Required
- Restrict access to the router management interface to trusted administrative networks and remove any exposure to the public internet
- Rotate credentials for all NX15 administrative accounts and enforce strong, unique passwords to raise the bar for the required authenticated access
- Audit recent access logs for the /api/esps endpoint and investigate any invocation of file.exec with suspicious arguments
Patch Information
At the time of publication, no vendor patch reference is listed in the NVD entry. Consult the VulDB CVE-2026-18900 advisory and H3C security bulletins for the latest firmware update covering V100R017. Apply firmware updates on all affected NX15 devices as soon as the vendor releases a fix.
Workarounds
- Place the management interface behind a jump host or VPN and block direct administrative access from user VLANs
- Disable remote management from WAN interfaces until a vendor-supplied firmware update is applied
- Apply access control lists that permit RPC endpoints only from designated administrator source addresses
# Example ACL restricting router management access to a trusted subnet
# Replace 10.10.0.0/24 with your administrative network
access-list mgmt-acl permit tcp 10.10.0.0/24 any eq 443
access-list mgmt-acl deny tcp any any eq 443
interface GigabitEthernet0/0
ip access-group mgmt-acl in
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
