dbcve.org
A3000ru FirmwareOperating system · Totolink

CVE-2025-4496

CRITICAL · 9.8 CVSS v3.1 Published 2025-05-10
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
A vulnerability was found in TOTOLINK T10, A3100R, A950RG, A800R, N600R, A3000RU and A810R 4.1.8cu.5241_B20210927. It has been declared as critical. This vulnerability affects the function CloudACMunualUpdate of the file /cgi-bin/cstecgi.cgi. The manipulation of the argument FileName leads to buffer overflow. The attack can be initiated remotely. The exploit has been disclosed to the public 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

A buffer overflow vulnerability exists in the CloudACMunualUpdate function of the TOTOLINK CGI binary (/cgi-bin/cstecgi.cgi) in firmware version 4.1.8cu.5241_B20210927. The vulnerability is triggered via the FileName argument and is exploitable remotely without authentication, allowing arbitrary code execution due to the heap/stack overflow condition.

MitigationApply vendor-supplied firmware patch when available; until then, disable the vulnerable CGI endpoint or restrict network access to the router's management interface to minimize attack surface.

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

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
A3000ru FirmwareOperating system
Affected:= 4.1.8cu.5241_b20210927
A810r FirmwareOperating system
Affected:= 4.1.8cu.5241_b20210927
T10 FirmwareOperating system
Affected:= 4.1.8cu.5241_b20210927
A3100r FirmwareOperating system
Affected:= 4.1.8cu.5241_b20210927
A950rg FirmwareOperating system
Affected:= 4.1.8cu.5241_b20210927
A800r FirmwareOperating system
Affected:= 4.1.8cu.5241_b20210927
N600r FirmwareOperating system
Affected:= 4.1.8cu.5241_b20210927

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
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/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. Identify device model
    Access the router's web interface or check the device label to determine the exact model (e.g., A3000ru, A810r, T10, A3100r, A950rg, A800r, N600r)
    Affected if Device is one of the listed Totolink models (A3000ru, A810r, T10, A3100r, A950rg, A800r, N600r)
  2. Check firmware version
    Log into the router administration panel and navigate to the firmware/version information page, or use the router's API if available, to retrieve the installed firmware version string
    Affected if Firmware version equals exactly 4.1.8cu.5241_B20210927
  3. Verify CGI binary presence
    Attempt to access the URL path /cgi-bin/cstecgi.cgi on the router (e.g., http://<router-ip>/cgi-bin/cstecgi.cgi) using an HTTP request
    Affected if The CGI binary responds to HTTP requests, indicating the vulnerable endpoint is exposed
  4. Check network exposure
    Determine if the router's management interface (HTTP/HTTPS ports) is accessible from untrusted networks by reviewing firewall rules or network configuration
    Affected if The router's web interface is reachable from wide-area or untrusted network segments without ACL restrictions

A user is affected if their Totolink device is one of the specified models running firmware version 4.1.8cu.5241_B20210927 and the CGI endpoint is network-accessible.

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-supplied firmware patch when available; until then, disable the vulnerable CGI endpoint or restrict network access to the router's management interface to minimize attack surface.

Fix this in A3000ru Firmware Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,900
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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-2025-4496 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