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Memory Buffer Bounds ErrorWeakness · CWE-119

CVE-2026-7749

HIGH · 8.8 CVSS v3.1 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 →
94/100
Remediation priority · Urgent
Remotely reachable 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
A security vulnerability has been detected in Totolink N300RH 3.2.4-B20220812. This affects the function setWanConfig of the file /cgi-bin/cstecgi.cgi of the component POST Request Handler. The manipulation of the argument priDns leads to buffer overflow. The attack may be initiated remotely. The exploit has been disclosed publicly and may be used.

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

Buffer overflow in Totolink N300RH router firmware (v3.2.4-B20220812) in the /cgi-bin/cstecgi.cgi CGI program. The setWanConfig function fails to properly validate the priDns parameter before copying it into a fixed-size buffer, allowing remote attackers to overflow the buffer and potentially execute arbitrary code via specially crafted HTTP POST requests.

MitigationApply vendor firmware patch if available; otherwise disable remote web administration, implement network segmentation to limit exposure to trusted networks, and monitor for exploitation attempts.

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 Totolink N300RH
    Access the router's web interface and check the device info page, or check the device label/marking. Alternatively, make a GET request to the CGI and inspect server headers for Totolink N300RH identification.
    Affected if The device is not a Totolink N300RH router, then this specific CVE does not apply.
  2. Verify the CGI endpoint exists and is accessible
    Send an HTTP GET request to http://<router-ip>/cgi-bin/cstecgi.cgi and check for a valid response. The endpoint should be reachable over the network.
    Affected if The CGI endpoint is unreachable or returns 404, the vulnerability cannot be exploited in its current state.
  3. Check if WAN configuration is exposed
    Review router web interface for WAN/Internet settings page. This is where the setWanConfig function would be called. Attempt a POST to the CGI with minimal parameters to confirm the function is accessible.
    Affected if The WAN configuration interface is disabled or not accessible, exploitation is not possible.
  4. Verify the priDns parameter is accepted
    Send a crafted HTTP POST to /cgi-bin/cstecgi.cgi with the setWanConfig action and an abnormally long priDns value (e.g., 500+ characters). Observe if the router accepts it without rejecting based on length.
    Affected if The priDns parameter is not accepted or is properly length-validated, the buffer overflow condition does not exist.
  5. Confirm web interface is network-accessible
    Determine if the router's administrative web interface (port 80/443) is exposed to untrusted networks. Check router firewall settings and NAT configuration.
    Affected if The web interface is only accessible from trusted LAN segments and not from WAN/internet-facing IPs, the remote attack vector is mitigated.

A user is affected if they operate a Totolink N300RH router with an accessible web CGI interface where the setWanConfig function accepts unchecked priDns input from network attackers.

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 patch if available; otherwise disable remote web administration, implement network segmentation to limit exposure to trusted networks, and monitor for exploitation attempts.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2026-7749 in production — separate from our analysis above.

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What this is

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