CVE-2026-108916

Executive Summary

CVE-2026-108916 is an OS command injection vulnerability in the Edimax BR-6208AC wireless router running firmware version 1.32. An attacker can remotely manipulate the submit-url argument handled by the /goform/formAccept endpoint, resulting in arbitrary command execution on the underlying operating system. The vendor was contacted but did not respond, the affected product is no longer supported, and a public exploit exists — leaving all internet-exposed devices permanently vulnerable with no official remediation path.

Technical Analysis

The vulnerability resides in the Edimax BR-6208AC's embedded web management interface. The device exposes a CGI-style handler at /goform/formAccept, the standard URL prefix used by the GoAhead/web-based configuration framework common to consumer routers. The handler processes an HTTP request argument named submit-url. According to the disclosure, manipulation of this argument allows an attacker to inject and execute operating-system-level commands.

The root cause maps to CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component, i.e., injection). In practice, this class of flaw manifests when user-supplied input is passed unsanitized into a shell interpreter, typically via functions such as system(), popen(), or exec() in the router's native binary or shell script backing the web endpoint. Special shell metacharacters (command separators, pipes, backticks, or command substitution sequences) embedded in the submit-url value are interpreted by the shell rather than treated as inert data, yielding command injection.

Key characteristics derived from the CVSS vector:

• Attack Vector: Network (AV:N) — the interface is reachable over the network.
• Attack Complexity: Low (AC:L) — no special conditions are required.
• Privileges Required: None (PR:N) — no authentication is mandated by the vector, meaning the endpoint is reachable without prior credentials (or the flaw is triggerable pre-authentication).
• User Interaction: None (UI:N) — fully automated exploitation.
• Scope: Changed (S:C) — the compromise of the web application component impacts resources beyond its security scope, consistent with escaping the web handler into the device OS.

The attack surface is the HTTP management plane. The vulnerability is remotely triggerable with a single crafted request. No public proof-of-concept code or Nuclei template is referenced in the provided data, so the exact injection syntax is not enumerated here; the mechanism is inferred from the injection class (CWE-74) and the confirmed affected parameter.

Because the firmware is unsupported, no upstream code review or patched binary exists to contrast against. This is a terminal, unpatchable condition for the 1.32 build.

Exploitation Scenarios

Note: No public PoC code, Nuclei template, or exploit code was provided in the source data. The following attack chain is inferred strictly from the vulnerability class (CWE-74 command injection) and the explicitly named endpoint and parameter.

1. Reconnaissance / Target Identification. An attacker scans internet-facing address space (e.g., via Shodan using the dorks above) for Edimax BR-6208AC devices exposing the web management interface. Devices with the /goform/ handler reachable and firmware 1.32 are flagged as candidates.

2. Triggering the Flaw. The attacker issues an HTTP request to /goform/formAccept, supplying the submit-url argument with a value crafted to include shell metacharacters. When the handler passes this value into an OS command without neutralization, the injected shell syntax is executed.

3. Payload / Execution. At the vulnerability-class level, a command-injection payload appends or embeds an arbitrary system command (e.g., a shell invocation) via standard shell separators or substitution. The specific payload string is not documented in the provided data and is not fabricated here. Successful execution confirms command-level control on the device OS.

4. Post-Exploitation Impact. With command execution under the web service's privilege context (often root on such devices), an attacker can read or alter configuration, establish persistence, pivot into the internal network, or recruit the device into a botnet. Because the vector shows Scope:Changed, the impact extends beyond the web application to the host OS and potentially the connected LAN.

Impact Assessment

• Confidentiality (Low): Attacker can read some device data and potentially adjacent network information, but the vector rates impact as partial.
• Integrity (Low): Configuration and stored data may be modified.
• Availability (Low): Services may be disrupted.
• Exploitability: Network-reachable, low complexity, no privileges, no user interaction — trivially automatable at scale.
• Blast radius: Any BR-6208AC at firmware 1.32 that is exposed to untrusted networks (internet-facing management interface or reachable from an untrusted LAN segment). Consumer/SOHO deployments where the router is the network edge represent the greatest risk, as device compromise yields a foothold at the network perimeter.
• Aggravating factors: Public exploit availability, no vendor patch, unsupported product, and changed scope (OS-level escape). These combine to make the effective risk significantly worse than the numeric score alone implies for exposed assets.

Detection Guidance

Sigma Rule

title: Edimax BR-6208AC Command Injection via submit-url
id: 3f9c1a2e-7b4d-4c8e-9a1f-2d6e5b8c0a33
status: experimental
description: Detects HTTP requests to the Edimax BR-6208AC /goform/formAccept endpoint with shell metacharacters in the submit-url parameter, indicating CVE-2026-108916 exploitation attempts.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-108916
author: valtersit.com
logsource:
  category: webserver
detection:
  selection_endpoint:
    cs-uri-stem|contains: '/goform/formAccept'
  selection_param:
    cs-uri-query|contains:
      - 'submit-url='
  selection_metachar:
    cs-uri-query|contains:
      - ';'
      - '|'
      - '`'
      - '$('
      - '&&'
  condition: selection_endpoint and selection_param and selection_metachar
falsepositives:
  - Legitimate administrative use of URLs containing encoded characters
level: high

YARA Rule

rule CVE_2026_108916_Edimax_CommandInjection
{
    meta:
        description = "Detects HTTP request patterns targeting Edimax BR-6208AC /goform/formAccept submit-url command injection (CVE-2026-108916)"
        author = "valtersit.com"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-108916"
        date = "2026-01-01"
        severity = "high"
    strings:
        $endpoint = "/goform/formAccept"
        $param    = "submit-url="
        $meta1    = "`"
        $meta2    = "$("
        $meta3    = ";wget"
        $meta4    = ";curl"
    condition:
        $endpoint and $param and any of ($meta*)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-108916 Edimax BR-6208AC Command Injection via submit-url"; flow:to_server,established; http.uri; content:"/goform/formAccept"; http.uri; content:"submit-url="; pcre:"/submit-url=[^&]*(%3B|;|%7C|\||%60|`|%24%28|\$\()/Ui"; classtype:web-application-attack; reference:cve,2026-108916; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-108916; sid:2026108916; rev:1;)

Elastic Detection

sequence by source.ip with maxspan=10s
  [ network where network.protocol == "http" and url.path == "/goform/formAccept" ]
  [ network where network.protocol == "http" and url.path == "/goform/formAccept" and
      url.query : ("submit-url=*;*" or "submit-url=*|*" or "submit-url=*`*" or "submit-url=*$(*") ]

Splunk SPL Query

index=web sourcetype=access_combined OR sourcetype=pan:traffic
| search uri_path="/goform/formAccept"
| eval inj=if(match(uri_query, "submit-url=.*(%3B|;|%7C|\||%60|`|%24%28|\$\()"), 1, 0)
| where inj=1
| stats count min(_time) as first_seen max(_time) as last_seen by src_ip, uri_query
| convert ctime(first_seen) ctime(last_seen)
| sort - count

Wazuh OSSEC Rule

<group name="web,edimax,cve-2026-108916,">
  <rule id="108916" level="12">
    <if_sid>31100</if_sid>
    <id>^/goform/formAccept</id>
    <match>submit-url=.*(%3B|;|%7C|\||%60|`|%24%28|\$\(|&&)</match>
    <description>CVE-2026-108916: Edimax BR-6208AC command injection attempt via /goform/formAccept submit-url</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>web_attack,command_injection,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 — UNPATCHED. No vendor fix exists; the affected product (BR-6208AC firmware 1.32) is end-of-life and the vendor did not respond to the disclosure. There is no official patch path.

1. Immediate mitigations (no official fix available):

   • Remove or block management-plane exposure. Restrict access to the web admin interface (/goform/ handlers) to a trusted management VLAN or trusted source IPs only.
   • Never expose the router's web management interface to the internet. If remote administration is required, place it behind a VPN.
   • Disable the HTTP management service entirely if it is not needed; prefer a protected out-of-band management path.
   • Apply network-level filtering (WAF/IPS signatures above) to block requests containing shell metacharacters in submit-url.
   • Segment or decommission affected devices; because the firmware is unsupported, treat them as untrusted.

2. Patch / upgrade steps:

   • No patch is available. Contact the vendor for a replacement or supported successor model. Monitor any vendor security advisory portal for future guidance in case the vendor reverses its non-response.
   • If a firmware update is ever released, validate it against the version currently deployed and apply immediately.

3. Long-term hardening:

   • Replace all end-of-life (EOL) network edge devices with vendor-supported hardware that receives security updates.
   • Establish a firmware lifecycle policy requiring an active support/maintenance window for all internet-adjacent devices.
   • Maintain an inventory of exposed management interfaces and continuously monitor with external attack-surface tools (Shodan, Censys) using the dorks above.
   • Enforce least-privilege access to device management and monitor for anomalous /goform/ request patterns.

References

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-108916
• CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component — Injection): https://cwe.mitre.org/data/definitions/74.html
• MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
• Vendor: Edimax BR-6208AC product/support site (no advisory issued; vendor did not respond to disclosure)
• CISA KEV: Not listed. No known threat actor campaign or confirmed in-the-wild exploitation evidence is available in the provided data; however, public exploit availability and the unpatched, unsupported nature of the device elevate risk for exposed units.