CVE-2026-76071: Stack Overflow (CVSS 9.8)

Description

Netis NC63 firmware through V3.0.0.3327 contains a stack-based buffer overflow vulnerability that allows unauthenticated remote attackers to overwrite saved stack state by supplying an oversized destHost parameter to the ipFilterList=mod action in netis.cgi. Attackers can exploit widthless sscanf conversions that copy user-supplied input into fixed-size stack buffers before authentication is verified, achieving remote code execution as root due to the Boa web server executing the CGI environment with root privileges.

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CVSS v3.1 Score

9.8

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0106

Probability of exploitation

0.63%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-121 CWE-121

References

Other References

https://github.com/ozcanpng/CVE-2026-76071 https://ozcanpng.dev/blog/cve-2026-76071-netis-nc63-ipfilter-stack-buffer-overflow/ https://www.netis-systems.com/products/NC63.html https://www.vulncheck.com/advisories/netis-nc63-stack-buffer-overflow-via-desthost-parameter

Frequently Asked Questions

What is CVE-2026-76071? +

Netis NC63 firmware through V3.0.0.3327 contains a stack-based buffer overflow vulnerability that allows unauthenticated remote attackers to overwrite saved stack state by supplying an oversized destHost parameter to the ipFilterList=mod action in netis.cgi. Attackers can exploit widthless sscanf conversions that copy user-supplied input into fixed-size stack buffers before authentication is verified, achieving remote code execution as root due to the Boa web server executing the CGI environment with root privileges. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-76071? +

CVE-2026-76071 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0106, placing it in the 1th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-76071? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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