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W6 S FirmwareOperating system · Tenda

CVE-2025-15255

CRITICAL · 9.8 CVSS v3.1 Published 2025-12-30
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
Public exploit 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 determined in Tenda W6-S 1.0.0.4(510). This impacts an unknown function of the file /bin/httpd of the component R7websSsecurityHandler. Executing a manipulation of the argument Cookie can lead to stack-based buffer overflow. The attack may be launched remotely. The exploit has been publicly disclosed and may be utilized.

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 · moderate confidence

A stack-based buffer overflow vulnerability exists in the Tenda W6-S router firmware version 1.0.0.4(510) within the /bin/httpd web server, specifically in the R7websSsecurityHandler component. By sending a specially crafted Cookie HTTP header with excessive data, an attacker can overflow a stack-based buffer and potentially achieve remote code execution on the device.

MitigationApply the latest Tenda firmware update for the W6-S model if available; otherwise, restrict network access to the router's web interface using firewall rules or network segmentation to prevent external attackers from sending malicious Cookie headers.

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
W6 S FirmwareOperating system
Affected:= 1.0.0.4\(510\)

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 and firmware version
    Access router admin interface or check firmware via telnet/SSH. Look for firmware version information in system status or via 'cat /proc/version' or 'nvram get firmware_version' if accessible.
    Affected if Firmware version is exactly 1.0.0.4(510)
  2. Verify httpd binary exists
    Check if /bin/httpd file exists on the device filesystem. This can be done via telnet/SSH access or by extracting firmware via binwalk.
    Affected if /bin/httpd is present on the device
  3. Determine if remote HTTP management is enabled
    Check router configuration for 'Remote Management' or 'Web Management' settings. Look for WAN-accessible HTTP/HTTPS ports via port scanning from outside the local network, or inspect iptables rules for port 80/443 bindings on WAN interfaces.
    Affected if Router web interface is accessible from WAN IP addresses on port 80/443
  4. Check for vulnerable Cookie parameter handling
    Send an HTTP request to the router's web interface with an abnormally long Cookie header (e.g., 500+ characters). Observe if the request causes unexpected behavior, crash, or unusual response.
    Affected if Device accepts and processes long Cookie parameters without crashing or rejecting them
  5. Verify network exposure of management interface
    Scan external IP address for open HTTP ports (80, 443, 8080). Check router firewall rules via 'iptables -L -n' or similar to see if INPUT chain allows connections to port 80 from WAN sources.
    Affected if HTTP management port is open to untrusted networks

The device is affected if it is a Tenda W6-S router running firmware version 1.0.0.4(510) with the httpd binary present and remote HTTP management accessible from untrusted networks.

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 the latest Tenda firmware update for the W6-S model if available; otherwise, restrict network access to the router's web interface using firewall rules or network segmentation to prevent external attackers from sending malicious Cookie headers.

Fix this in W6 S Firmware Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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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-2025-15255 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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