Wavlink WL-NU516U1 nas.cgi ftext stack-based overflow

published 2026-03-26 7 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-16146

cvss: 8.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.9%; EPSS 0.9% chance of exploitation in 30 days, percentile 58%
public exploits: 0; none known

A weakness has been identified in Wavlink WL-NU516U1 260227. This vulnerability affects the function ftext of the file /cgi-bin/nas.cgi. This manipulation of the argument Content-Length causes stack-based buffer overflow. The attack can be initiated remotely. The exploit has been made available to the public and could be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: total
Assessed: 7 mo ago (2026-03-26)

Exploit prediction

0.86% chance of exploitation in the next 30 days, higher than 58% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/Wlz1112/WAVLINK-NU516U1-V260227/blob/main/Content-Length.md referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	4.0	8.7	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P
CNA	3.1	8.8	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:X/RC:R
CNA	3.0	8.8	CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:X/RC:R
CNA	2.0	9.0	AV:N/AC:L/Au:S/C:C/I:C/A:C/E:POC/RL:ND/RC:UR
CNA	4.0	7.4	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CNA	3.1	8.8	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CNA	2.0	9.0	AV:N/AC:L/Au:S/C:C/I:C/A:C

Affected products

Wavlink WL-NU516U1

Classification

Weakness

CWE-121 Stack-based Buffer Overflow
CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer

References

github.com /Wlz1112/WAVLINK-NU516U1-V260227/blob/main/Content-Length.md
exploit, third-party-advisory
vuldb.com /?id.353192
vdb-entry, technical-description, third-party-advisory
vuldb.com /?ctiid.353192
signature, permissions-required, vdb-entry
vuldb.com /?submit.776217
third-party-advisory, vdb-entry

Sources

CVE List CVE-2026-4861
NVD CVE-2026-4861

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary