# CVE-2026-36779: Tenda O3 Wireless Router stack overflow in fromVirtualSer

Source: https://junglewise.ai/threats/cve-2026-36779-tenda-o3-wireless-router-stack-overflow-in-fromvirtualser  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-09. Updated: 2026-06-09  
License: CC BY 4.0 with a link back

CVE-2026-36779 · Severity: info · CVSS 7.5 · Published 2026-06-09

The Tenda O3 Wireless Router, used for long-range outdoor wireless networking, contains a security flaw in its web management interface. By sending a specially crafted web request to the device, an attacker can cause the router to crash or reboot. This results in a denial of service, disrupting internet connectivity and network operations for all connected users.

Technologies: [Tenda O3 Wireless Router](https://junglewise.ai/threats/technologies/o3). Vendors: [Tenda](https://junglewise.ai/threats/vendors/tenda).

## Quick answers

**Is CVE-2026-36779 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-36779 being exploited in the wild.

**How severe is CVE-2026-36779?** Informational severity, with a CVSS score of 7.5, published 9 June 2026.

**Which products and versions are affected?** Tenda O3 Wireless Router v1.0.0.5(4180).

**Is there a fix for CVE-2026-36779?** 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-2026-36779 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-36779?** Check whether you run Tenda O3 Wireless Router 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

Multiple stack-based buffer overflows exist in the 'fromVirtualSer' CGI handler of the Tenda O3 router (firmware v1.0.0.5). The vulnerability is located in the 'fromVirtualSer' function, where user-supplied parameters (puVar2, puVar1, __s2, __s1_00, and puVar3) are retrieved via 'websGetVar' and subsequently passed to 'sprintf' without length validation. An attacker can exploit this by sending a crafted HTTP request with overly long strings in these parameters to overwrite the stack. While the primary reported impact is a Denial of Service (DoS) through device crashes, stack exhaustion of this nature often carries a risk of arbitrary code execution. The vulnerability is reachable over the network via the web management interface.

## Affected products

- Tenda O3 Wireless Router v1.0.0.5(4180)

## Timeline

- 2026-03-10: other: CVE request submitted to MITRE
- 2026-06-06: disclosed: Public disclosure
- 2026-06-09: advisory: NVD published date

## References

- [https://github.com/xhh0124/SemVulLLM/tree/main/O3/fromVirtualSer](https://github.com/xhh0124/SemVulLLM/tree/main/O3/fromVirtualSer)

## Related threats

- [Tenda O3 Wireless Router stack overflow in fromNetToolGet](https://junglewise.ai/threats/cve-2026-36784-tenda-o3-wireless-router-stack-overflow-in-fromnettoolget)
- [Tenda O3 Wireless Router stack overflow in fromNetToolGet](https://junglewise.ai/threats/cve-2026-36783-tenda-o3-wireless-router-stack-overflow-in-fromnettoolget)
- [Tenda O3 Wireless Router stack overflow in R7WebsSecurityHandler](https://junglewise.ai/threats/cve-2026-36778-tenda-o3-wireless-router-stack-overflow-in-r7webssecurityhandler)