Critical Memory corruption

CVE-2026-18588 — Wavlink WL-NU516U1 nas.cgi fgets stack-based overflow

A vulnerability has been found in Wavlink WL-NU516U1 708c073-mt7628. This affects the function fgets of the file nas.cgi. The manipulation of the argument CONTENT_LENGTH leads to stack-based buffer overflow. Remote exploitation of the attack is possible. You should upgrade the affected component. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.

Published Aug 3, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: VulDB

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

Technical severity (critical)+10
CISA SSVC: exploitation "poc"+5
Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

Wavlink

WL-NU516U1

CVSS base

9.8

Critical · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

Proof of concept

none · proof-of-concept · active

Automatable

Yes

can an attacker script the kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Wavlink WL-NU516U1).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Wavlink	WL-NU516U1	version 708c073-mt7628	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
9.3	CVSS 4.0	Critical	—	—	cna@vuldb.com via NIST National Vulnerability Database
9.3	CVSS 4.0	Critical	—	—	VulDB via CVE Program (cve.org) e CISA ADP
9.8	CVSS 3.1	Critical	3.9	5.9	cna@vuldb.com via NIST National Vulnerability Database
9.8	CVSS 3.1	Critical	—	—	VulDB via CVE Program (cve.org) e CISA ADP
9.8	CVSS 3.0	Critical	—	—	VulDB via CVE Program (cve.org) e CISA ADP
10.0	CVSS 2.0	High	10.0	10.0	cna@vuldb.com via NIST National Vulnerability Database
10.0	CVSS 2.0	High	—	—	VulDB via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: cna@vuldb.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-119 · Buffer Errors (Improper Restriction of Operations within Memory Bounds)

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.

web/proxy/WAF logsnetwork IDS/IPSendpoint telemetry (EDR)crash dumps

Timeline

What happened to this CVE, newest first.

2026
Affected products added · wavlink/wl-nu516u1
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 15, 2026
CVSS changed · 9.8
Oct 15, 2026 · NIST National Vulnerability Database
Source status changed · → Deferred
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Aug 3, 2026 · VulDB

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

6 on the record

dl.wavlink.com/firmware/RD/WINSTAR_NU516U1-WO-A-2026-07-13-4b8a21f-mt7628-squashfs-s
broken-link, patch, NIST National Vulnerability Database
vuldb.com/vuln/385416/cti
signature, permissions-required, NIST National Vulnerability Database
vuldb.com/cve/CVE-2026-18588
third-party-advisory, NIST National Vulnerability Database
vuldb.com/vuln/385416
vdb-entry, technical-description, NIST National Vulnerability Database
vuldb.com/submit/850500
third-party-advisory, NIST National Vulnerability Database
github.com/oduoke567/WAVLINK-NU516U1-2026-05-1/blob/main/report2.md
broken-link, NIST National Vulnerability Database

Elsewhere on this site

Wavlink
every CVE for this vendor

Memory corruption
same class

CWE-119
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2026-18590 Wavlink WL-NU516U1 Admin Password adm.cgi set_sys_adm os command injection Aug 3, 2026
Medium CVE-2026-15513 Wavlink WL-NU516U1 adm.cgi wlink_uci_set_value os command injection Jul 12, 2026
High CVE-2026-4861 Wavlink WL-NU516U1 nas.cgi ftext stack-based overflow Mar 26, 2026
Low CVE-2026-4166 Wavlink WL-NU516U1 login.cgi sub_404F68 cross site scripting Mar 16, 2026
High CVE-2026-3662 Wavlink WL-NU516U1 adm.cgi usb_p910 command injection Mar 7, 2026
High CVE-2026-3661 Wavlink WL-NU516U1 adm.cgi ota_new_upgrade command injection Mar 7, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No FIRST EPSS score.
No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-18588 is "Wavlink WL-NU516U1 nas.cgi fgets stack-based overflow", rated Critical. It affects WL-NU516U1 (Wavlink); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.8 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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