TOTOLINK X2000R: Stack-based buffer overflow in boa formFilter via vpnUser
Summary
The boa web management interface of the TOTOLINK X2000R router (firmware TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327) contains a stack-based buffer overflow in the formFilter handler. The vpnUser POST parameter is copied to a fixed-size stack buffer without a length check when a non-empty addFilterIp value is supplied. An authenticated attacker can send a crafted HTTP request to overwrite memory and may execute arbitrary code on the device.
Affected
- TOTOLINK X2000R, firmware TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327
- Other firmware versions: Unknown.
Fixed in
Unknown.
Workaround
- No vendor workaround known.
- Restrict access to the web management interface to a trusted management LAN and block it from WAN.
- Disable VPN features if they are not used.
Exploitation
- No known exploitation in the wild; not listed in CISA KEV.
- No public proof of concept found.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- Exploitation requires valid authentication with high privileges.
Our recommendation
- Check whether any TOTOLINK X2000R is reachable from the internet; if so, remove that exposure immediately.
- Inventory X2000R devices and their firmware versions.
- Check the TOTOLINK support site for a firmware update and ask the vendor for a fix date.
- Use strong, unique administrator passwords and monitor administrative logins.
- Re-check NVD and CISA KEV in one week, as the NVD status is Deferred.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Cisco Talos TALOS-2026-2425 talosintelligence.com
- OpenCVE CVE-2026-9659 app.opencve.io
- CVE-2026-9659 on threatint cve.threatint.com
- Strix CVE-2026-9659 www.strix.ai
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 31 Oct 2026, 05:52.
Original description (NVD)
Multiple exploitable stack-based buffer overflow vulnerabilities exist in the boa formFilter functionality of X2000R (version(s): TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327). A specially crafted HTTP request can lead to arbitrary code execution. An attacker can make an authenticated HTTP request to trigger these vulnerabilities. This vulnerability deals with the vpnUser parameter.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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