CVE-2025-3543: H3C Magic Router RCE Vulnerability

CVE-2025-3543 Overview

CVE-2025-3543 is a command injection vulnerability affecting H3C Magic NX15, Magic NX30 Pro, Magic NX400, and Magic R3010 routers running firmware up to V100R014. The flaw resides in the FCGI_WizardProtoProcess function within the /api/wizard/setsyncpppoecfg endpoint of the HTTP POST request handler. Attackers with local network access and low privileges can inject arbitrary operating system commands by manipulating request parameters. The exploit has been publicly disclosed, increasing the likelihood of opportunistic abuse against exposed devices. The weakness is tracked under CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component).

Critical Impact
Successful exploitation grants attackers command execution on the router, enabling full device compromise, traffic interception, and lateral movement across the local network.

Affected Products

H3C Magic NX15 (firmware up to V100R014)
H3C Magic NX30 Pro and Magic NX400 (firmware up to V100R014)
H3C Magic R3010 (firmware up to V100R014)

Discovery Timeline

2025-04-14 - CVE-2025-3543 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-3543

Vulnerability Analysis

The vulnerability exists in the FCGI_WizardProtoProcess function, which handles PPPoE configuration synchronization through the /api/wizard/setsyncpppoecfg endpoint. The FastCGI handler parses HTTP POST parameters and passes user-controlled values into a downstream system command without proper neutralization of shell metacharacters. An adjacent attacker submits a crafted POST request containing shell operators such as backticks, semicolons, or command substitution syntax. The router executes the injected commands with the privileges of the web management process, which on embedded H3C devices typically runs as root.

The attack requires only local network adjacency and authenticated low-privileged access. Because home and small-office routers frequently use default or weak credentials, the privilege prerequisite is not a strong barrier. A public proof-of-concept has been released on GitHub, lowering the technical bar for exploitation.

Root Cause

The root cause is missing input sanitization in the wizard configuration handler. The FCGI_WizardProtoProcess function forwards user-supplied PPPoE parameters directly into a shell invocation, permitting metacharacter interpretation by the underlying command interpreter. This is a classic instance of [CWE-74] where output encoding is absent before data crosses a trust boundary into the operating system shell.

Attack Vector

Exploitation requires network adjacency to the target router, typically through Wi-Fi association or a wired LAN connection. The attacker authenticates to the web management interface with any valid low-privileged account and then issues a crafted POST request to /api/wizard/setsyncpppoecfg. The injected payload executes on the router immediately, enabling persistence installation, DNS hijacking, configuration exfiltration, or pivoting to other devices on the LAN.

A public proof-of-concept demonstrating request construction is available. See the GitHub Gist PoC and the VulDB Analysis #304582 for technical details.

Detection Methods for CVE-2025-3543

Indicators of Compromise

HTTP POST requests to /api/wizard/setsyncpppoecfg containing shell metacharacters such as ;, |, &&, backticks, or $( in body parameters.
Unexpected outbound connections initiated by the router to attacker-controlled infrastructure following wizard endpoint access.
New or modified files under writable firmware paths, or unexpected processes spawned by the web management daemon.

Detection Strategies

Deploy network intrusion detection signatures that match POST bodies to /api/wizard/ endpoints containing command separators or substitution syntax.
Correlate router administrative HTTP access with subsequent anomalous DNS, proxy, or SSH activity originating from the device.
Monitor authentication logs on the H3C management interface for logins from unfamiliar LAN clients preceding wizard configuration changes.

Monitoring Recommendations

Capture and inspect LAN-side HTTP traffic directed at router management interfaces to identify wizard endpoint abuse.
Alert on router configuration changes outside authorized change windows, particularly PPPoE and DNS settings.
Baseline expected outbound connections from router IP addresses and flag deviations that suggest command-and-control activity.

How to Mitigate CVE-2025-3543

Immediate Actions Required

Upgrade affected H3C Magic routers to firmware newer than V100R014 once the vendor publishes a fix through the H3C Document Download portal.
Restrict access to the router web management interface to trusted administrative hosts only; disable management from wireless SSIDs where feasible.
Rotate all administrative credentials on affected devices and eliminate default or shared low-privileged accounts that could be leveraged to reach the vulnerable endpoint.

Patch Information

H3C has not published a specific patch identifier tied to CVE-2025-3543 in the referenced advisories at the time of writing. Consult the H3C Product Details page and the H3C download portal for firmware releases superseding V100R014. Until a fixed firmware image is available, treat all affected devices as vulnerable and apply compensating controls.

Workarounds

Segment the LAN so that untrusted clients, guest Wi-Fi, and IoT devices cannot reach the router administrative interface on TCP/80 or TCP/443.
Disable the setup wizard endpoint via ACLs on upstream network equipment if the router does not expose a configuration option to turn it off.
Enforce strong, unique administrator credentials and require re-authentication for wizard operations to reduce opportunistic abuse by low-privileged LAN users.

bash

# Example ACL restricting router management to a single admin workstation
# Applied on an upstream managed switch or firewall
access-list MGMT_ONLY permit tcp host 192.0.2.10 host 192.0.2.1 eq 80
access-list MGMT_ONLY permit tcp host 192.0.2.10 host 192.0.2.1 eq 443
access-list MGMT_ONLY deny   tcp any host 192.0.2.1 eq 80
access-list MGMT_ONLY deny   tcp any host 192.0.2.1 eq 443
access-list MGMT_ONLY permit ip any any