CVE-2026-2566
Published: 16 February 2026
Summary
CVE-2026-2566 is a high-severity Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119) vulnerability. Its CVSS base score is 7.3 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 18.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-16 (Memory Protection).
Deeper analysis
CVE-2026-2566 is a stack-based buffer overflow vulnerability (CWE-119, CWE-121) affecting Wavlink WL-NU516U1 firmware versions up to 130/260. The issue resides in the sub_406194 function within the /cgi-bin/adm.cgi script, where improper handling of the firmware_url argument enables the overflow. Published on 2026-02-16, it carries a CVSS v3.1 base score of 7.2 (AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H).
The vulnerability is exploitable remotely over the network by authenticated attackers possessing high privileges on the target device. Exploitation requires low complexity and no user interaction, allowing successful attackers to achieve high impacts across confidentiality, integrity, and availability, such as arbitrary code execution or denial of service.
Advisories from VulDB and a related GitHub repository detail the vulnerability and confirm that a public exploit has been disclosed. The vendor was notified early regarding the issue but provided no response, and no patches or official mitigations are referenced in the available sources. Security practitioners should isolate affected devices and monitor for anomalous firmware update attempts until further vendor guidance emerges.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-7664
Vulnerability details
A security vulnerability has been detected in Wavlink WL-NU516U1 up to 130/260. This affects the function sub_406194 of the file /cgi-bin/adm.cgi. Such manipulation of the argument firmware_url leads to stack-based buffer overflow. The attack can be launched remotely. The exploit…
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has been disclosed publicly and may be used. The vendor was contacted early about this disclosure but did not respond in any way.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Stack-based buffer overflow in public-facing /cgi-bin/adm.cgi (firmware_url) enables remote authenticated RCE on Linux-based router firmware, directly mapping to exploitation of public-facing applications and Unix shell command execution.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly enforces validation of the firmware_url argument in adm.cgi to block the oversized input that triggers the stack overflow.
Applies memory-protection mechanisms that can prevent exploitation of the stack-based buffer overflow even if malformed input reaches sub_406194.
Limits the high-privilege accounts that can reach /cgi-bin/adm.cgi, reducing the population able to supply the malicious firmware_url parameter.