# CVE-2026-76861: Netcore NR255-V stack buffer overflow in ntools_tcpdump_start_set.cgi

Source: https://junglewise.ai/threats/cve-2026-76861-netcore-nr255-v-stack-buffer-overflow-in-ntools-tcpdump-start-set  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-15. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-76861 · Severity: high · CVSS 8.8 · Published 2026-09-15

Netcore NR255-V is a router device used to manage network connectivity in business and home environments. A stack buffer overflow vulnerability in its web administration interface allows authenticated attackers to submit specially crafted input that crashes the router or executes malicious code with full device privileges, potentially compromising network traffic monitoring and customer data.

Technologies: [Netcore NR255-V](https://junglewise.ai/threats/technologies/nr255-v). Vendors: [Netcore](https://junglewise.ai/threats/vendors/netcore).

## Quick answers

**Is CVE-2026-76861 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-76861 being exploited in the wild.

**How severe is CVE-2026-76861?** High severity, with a CVSS score of 8.8, published 15 September 2026.

**Which products and versions are affected?** Netcore NR255-V 1.5.130703.

**Is there a fix for CVE-2026-76861?** 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-2026-76861 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-76861?** Check whether you run Netcore NR255-V 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 stack-based buffer overflow (CWE-121) exists in the ntools_tcpdump_start_set.cgi endpoint due to an unsized sprintf call that does not validate the length of user-supplied form values before copying them into a fixed-size stack buffer. The vulnerable code path is in ntools_tcpdump_start_set_cgi.c (at offset 0x46b3f8) and calls get_form_value.c (0x407100). Attack requires network access and authentication to the device's web interface, but no user interaction. Exploitation allows an attacker to overflow the stack buffer and achieve arbitrary code execution with the privileges of the web server process. A patch or mitigation has not been confirmed as available at this time.

## Affected products

- Netcore NR255-V 1.5.130703

## Timeline

- 2026-09-04: disclosed
- 2026-09-15: advisory: CVE-2026-76861 published

## References

- [https://github.com/draw-ctf/netcore-router-public-refs/blob/main/2026.08.19-netcore-nr255v-tcpdump-overflow.md](https://github.com/draw-ctf/netcore-router-public-refs/blob/main/2026.08.19-netcore-nr255v-tcpdump-overflow.md)
- [https://www.vulncheck.com/advisories/netcore-nr255-v-1.5.130703-stack-based-buffer-overflow-in-ntools-tcpdump-start-set-cgi](https://www.vulncheck.com/advisories/netcore-nr255-v-1.5.130703-stack-based-buffer-overflow-in-ntools-tcpdump-start-set-cgi)

## Related threats

- [Netcore NR255-V stored cross-site scripting in L7 content management](https://junglewise.ai/threats/cve-2026-92257-netcore-nr255-v-stored-cross-site-scripting-in-l7-content)
- [Netcore NR255-V sensitive information disclosure in VPN configuration handlers](https://junglewise.ai/threats/cve-2026-92256-netcore-nr255-v-sensitive-information-disclosure-in-vpn)
- [Netcore NR255-V out-of-bounds read in filter_arp_put_file.cgi](https://junglewise.ai/threats/cve-2026-92255-netcore-nr255-v-out-of-bounds-read-in-filter-arp-put-file-cgi)
- [Netcore NR255-V stored cross-site scripting in DHCP and ARP hostname fields](https://junglewise.ai/threats/cve-2026-76873-netcore-nr255-v-stored-cross-site-scripting-in-dhcp-and-arp)
- [Netcore NR255-V stored cross-site scripting in DHCP and ACL management](https://junglewise.ai/threats/cve-2026-76872-netcore-nr255-v-stored-cross-site-scripting-in-dhcp-and-acl)