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Memory Buffer Bounds ErrorWeakness · CWE-119

CVE-2026-13539

HIGH · 8.8 CVSS v3.1 Published 2026-06-29
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
94/100
Remediation priority · Urgent
Remotely reachable Zero-click 7 weeks old

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
A vulnerability was identified in Wavlink WL-NU516U1-A M16U1_V240425. The impacted element is the function sub_407504 of the file /cgi-bin/wireless.cgi of the component POST Parameter Handler. Such manipulation of the argument Guest_ssid leads to stack-based buffer overflow. The attack can be executed remotely. The exploit is publicly available and might be used. It is suggested to upgrade the affected component. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.

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

A stack-based buffer overflow vulnerability exists in the Wavlink WL-NU516U1-A router's wireless.cgi POST parameter handler (function sub_407504). The Guest_ssid parameter is not properly bounds-checked before being copied to a stack buffer, allowing remote attackers to overwrite return addresses and potentially execute arbitrary code.

MitigationUpgrade the Wavlink WL-NU516U1-A to the vendor's patched firmware version to remediate this stack-based buffer overflow in the wireless.cgi component.

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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 Wavlink WL-NU516U1-A
    Access the router admin interface or check the device label/marketing materials to verify the exact model number matches WL-NU516U1-A
    Affected if The device is not a Wavlink WL-NU516U1-A router - other models are not affected by this specific vulnerability
  2. Check if wireless.cgi is present and accessible
    Attempt to access the URI /cgi-bin/wireless.cgi via HTTP or HTTPS on the router's LAN or WAN IP address
    Affected if The wireless.cgi endpoint does not exist or returns a 404 error - the vulnerable code path is not present
  3. Verify Guest SSID functionality is enabled
    Log into the router admin panel and navigate to the wireless settings to check if a Guest SSID (or Guest WiFi) has been configured or enabled
    Affected if Guest SSID feature is disabled/not configured - the vulnerable parameter handler may not be exercised in normal operation
  4. Check firmware version if accessible
    Look in the router admin interface under System Settings, Status, or Firmware Upgrade page for the installed firmware version number
    Affected if Unable to determine firmware version for comparison - the specific vulnerable version range is not specified in public advisories

The environment is affected only if the device is a Wavlink WL-NU516U1-A router with the wireless.cgi endpoint accessible and the Guest SSID feature in use, allowing the unbounded Guest_ssid parameter to trigger the stack overflow in function sub_407504.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade the Wavlink WL-NU516U1-A to the vendor's patched firmware version to remediate this stack-based buffer overflow in the wireless.cgi component.

Recommended fix Moderate confidence
  1. Identify the current firmware version of the Wavlink WL-NU516U1-A device (reportedly M16U1_V240425)
  2. Visit the official Wavlink download page at dl.wavlink.com to obtain the latest firmware version
  3. Download the most recent firmware release for the WL-NU516U1-A model
  4. Follow the manufacturer's standard firmware upgrade procedure (typically via web UI at http://192.168.1.1 or similar)
  5. After upgrading, verify the Guest_ssid parameter handling in /cgi-bin/wireless.cgi no longer exhibits overflow behavior
  6. Confirm the new firmware version is applied

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA2.0 h
9.0 hours of engineering $1,570
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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-2026-13539 in production — separate from our analysis above.

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