Buffer overflow in Netcore Nr256cn
CVE-2026-111711
Netcore NR256CN through 1.5.140116 contains a pre-authentication stack overflow vulnerability in the Boa web server's user_ok() function, which copies Basic-auth usernames with unbounded strcpy() calls into 64-byte stack buffers. Unauthenticated attackers can send a username longer than 63 bytes to any protected /router/*.cgi route to crash the main Boa process or potentially execute code.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/lukadqq/netcore-router-public-refs/blob/a44d562736b41c944223297e9144… (third-party-advisory)
- VulnCheck Advisory: Netcore NR256CN through 1.5.140116 Pre-Auth Stack Overflow via Boa user_ok() (third-party-advisory)
Frequently asked questions
- What is CVE-2026-111711?
- CVE-2026-111711 is a critical-severity vulnerability in Netcore Nr256cn, classified under Stack-based Buffer Overflow. CVSS score: 9.8/10. Published 2026-10-16.
- How severe is CVE-2026-111711?
- Critical severity. CVSS v3 base score is 9.8 out of 10.