CVE-2026-4861Public exploitNetwork attack vector

Authenticated code execution via unchecked HTTP body length

Published Mar 26, 2026 · Updated Mar 26, 2026

Stack-based buffer overflow in Wavlink WL-NU516U1 260227 allows remote authenticated users to execute code via a crafted HTTP request. The ftext function in /cgi-bin/nas.cgi converts CONTENT_LENGTH to a read size and passes it to fgets for a fixed 516-byte stack buffer without bounds checking. A valid session cookie is required; an oversized Content-Length and matching POST body overwrite saved stack state, causing a crash or attacker-controlled execution.

CVSS severity8.8
High
EPSS probability0.85%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in Wavlink WL-NU516U1 260227 allows remote authenticated users to execute code via a crafted HTTP request. The ftext function in /cgi-bin/nas.cgi converts CONTENT_LENGTH to a read size and passes it to fgets for a fixed 516-byte stack buffer without bounds checking. A valid session cookie is required; an oversized Content-Length and matching POST body overwrite saved stack state, causing a crash or attacker-controlled execution.

The record

CVE
CVE-2026-4861
Published
Mar 26, 2026
Updated
Mar 26, 2026
Vendor
Wavlink
Product
WL-NU516U1
Classifications
CWE-121, CWE-119, T1210
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=260227

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Wavlink · WL-NU516U1version=260227

Published CVSS scores

9.0VulDBAV:N/AC:L/Au:S/C:C/I:C/A:C
7.4VulDBCVSS: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
8.8VulDBCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1210Exploitation of Remote Services

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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