# CVE-2026-85109: Tenda HG10 buffer overflow in Boa Web Server login handler

Source: https://junglewise.ai/threats/cve-2026-85109-tenda-hg10-buffer-overflow-in-boa-web-server-login-handler  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-03. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-85109 · Severity: critical · CVSS 9.8 · Published 2026-09-03

The Tenda HG10 router contains a web server component vulnerable to buffer overflow when processing login requests. An unauthenticated attacker can send a specially crafted HTTP request with an oversized username parameter to crash the device or potentially execute arbitrary code, disrupting network connectivity for all users relying on that router.

Technologies: [Tenda HG10](https://junglewise.ai/threats/technologies/hg10). Vendors: [Tenda](https://junglewise.ai/threats/vendors/tenda).

## Quick answers

**Is CVE-2026-85109 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-85109 being exploited in the wild.

**How severe is CVE-2026-85109?** Critical severity, with a CVSS score of 9.8, published 3 September 2026.

**Which products and versions are affected?** Tenda HG10 HG7_HG9_HG10re_300001138.

**Is there a fix for CVE-2026-85109?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-85109 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-85109?** Check whether you run Tenda HG10 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A buffer overflow vulnerability exists in the Boa Web Server's formLogin function (/boaform/formLogin) within the Tenda HG10 router. The vulnerability arises from unsafe handling of the username parameter, which is copied into a fixed-size buffer using strcpy() without length validation. An attacker can craft an HTTP POST request to /boaform/formLogin with an oversized username parameter, causing a stack buffer overflow. No authentication is required; the attack is remotely exploitable over the network. Exploitation has been demonstrated to cause denial-of-service (device crash), and depending on memory layout and runtime protections, could potentially enable arbitrary code execution. The vulnerability affects firmware version 300001138 and has been publicly disclosed with proof-of-concept code available.

## Affected products

- Tenda HG10 HG7_HG9_HG10re_300001138

## Timeline

- 2026-09-03: disclosed: Publicly disclosed via GitHub and NVD
- 2026-09-03: other: CVE-2026-85109 assigned

## References

- [https://github.com/SunnyYANGyaya/cuicuishark-sheep-fishIOT/blob/main/Tenda/HG10/bof-formLogin_username.md](https://github.com/SunnyYANGyaya/cuicuishark-sheep-fishIOT/blob/main/Tenda/HG10/bof-formLogin_username.md)
- [https://vuldb.com/cve/CVE-2026-85109](https://vuldb.com/cve/CVE-2026-85109)

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- [Tenda HG10 OS command injection in formgponConf](https://junglewise.ai/threats/cve-2026-86167-tenda-hg10-os-command-injection-in-formgponconf)
- [Tenda HG10 buffer overflow in formWanRedirect](https://junglewise.ai/threats/cve-2026-86166-tenda-hg10-buffer-overflow-in-formwanredirect)
- [Tenda HG10 buffer overflow in formURL](https://junglewise.ai/threats/cve-2026-86165-tenda-hg10-buffer-overflow-in-formurl)
- [Tenda HG10 buffer overflow in formWlanSetup SSID parameter](https://junglewise.ai/threats/cve-2026-85110-tenda-hg10-buffer-overflow-in-formwlansetup-ssid-parameter)