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OS Command InjectionWeakness · CWE-78

CVE-2026-41926

CRITICAL · 9.3 CVSS v4.0 Published 2026-05-04
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
WDR201A WiFi Extender (HW V2.1, FW LFMZX28040922V1.02) contains an OS command injection vulnerability in the firewall.cgi binary across five request handlers that apply insufficient input validation. Attackers can inject arbitrary shell commands through vulnerable parameters like websURLFilter, websHostFilter, portForward, singlePortForward, and ipportFilter using subshell syntax or unfiltered parameters, with payloads persisting in NVRAM and re-executing on every subsequent firewall.cgi request.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

OS command injection vulnerability in WDR201A WiFi Extender's firewall.cgi binary allows arbitrary shell command execution through five parameters (websURLFilter, websHostFilter, portForward, singlePortForward, ipportFilter) with payloads persisting in NVRAM and re-executing on each request.

MitigationApply vendor firmware update if available; otherwise isolate device on restricted network segment or replace device entirely, as embedded devices often lack patches for legacy vulnerabilities.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
Authentication
X
User interaction
None
Scope
X

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm device model is WDR201A
    Access the device's web admin interface or check the device label/metadata to verify the exact model number
    Affected if Device is not a WDR201A WiFi Extender, then likely not affected by this specific CVE
  2. Identify firmware version
    Log into the device admin panel (typically at 192.168.0.1 or 192.168.1.1) and navigate to Status or System settings to view the firmware version
    Affected if Firmware version is unknown or falls within the range where this command injection vulnerability exists (compare against vendor release notes for patches)
  3. Inspect NVRAM for malicious entries
    Access the device via SSH or Telnet if enabled, then run 'nvram show' or 'grep' for the affected parameter names (websURLFilter, websHostFilter, portForward, singlePortForward, ipportFilter) to see if they contain shell metacharacters like ; | & $ or unusual command strings
    Affected if NVRAM contains any of these parameters with command-like content (shell commands, URLs with suspicious patterns, IP addresses combined with operators)
  4. Check firewall.cgi accessibility and behavior
    Send a crafted HTTP request to the firewall.cgi endpoint using one of the five affected parameters (e.g., http://<device_ip>/cgi-bin/firewall.cgi?websURLFilter=test) and observe if commands execute or return unexpected output
    Affected if The device responds to these parameter queries and exhibits unexpected behavior suggesting command execution
  5. Review device logs for suspicious activity
    Check system logs, web server logs, or NVRAM logs for any entries containing the five affected parameter names combined with shell syntax or repeated identical requests
    Affected if Logs show repeated requests to these parameters or entries containing shell command patterns

A user is affected if they own a WDR201A WiFi Extender with unpatched firmware, and NVRAM inspection or log analysis reveals the vulnerable parameters contain injected commands or exhibit unexpected execution behavior.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply vendor firmware update if available; otherwise isolate device on restricted network segment or replace device entirely, as embedded devices often lack patches for legacy vulnerabilities.

Have this fixed Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA3.0 h
27.0 hours of engineering $4,800
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-41926 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data