CVE-2026-1637Public exploitNetwork attack vector

Authenticated code execution via unchecked stack copy

Published Jan 29, 2026 · Updated Jan 29, 2026

Stack-based buffer overflow in Tenda AC21 Firmware 16.03.08.16 allows remote authenticated users to execute arbitrary code via a POST request. The sub_44C7A8 helper called by fromAdvSetMacMtuWan passes an unbounded serverName value from websGetVar to strcpy, overwriting a fixed stack buffer. Low-privileged access to the web management interface is required; exploitation can crash httpd or overwrite its return address to take control.

CVSS severity8.8
High
EPSS probability0.66%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

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Summary

What happened

Stack-based buffer overflow in Tenda AC21 Firmware 16.03.08.16 allows remote authenticated users to execute arbitrary code via a POST request. The sub_44C7A8 helper called by fromAdvSetMacMtuWan passes an unbounded serverName value from websGetVar to strcpy, overwriting a fixed stack buffer. Low-privileged access to the web management interface is required; exploitation can crash httpd or overwrite its return address to take control.

The record

CVE
CVE-2026-1637
Published
Jan 29, 2026
Updated
Jan 29, 2026
Vendor
Shenzhen Tenda Technology Co., Ltd.
Product
AC21 Firmware
Classifications
CWE-121, CWE-119, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 29, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 29, 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=16.03.08.16

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Shenzhen Tenda Technology Co., Ltd. · AC21 Firmwareversion=16.03.08.16

Published CVSS scores

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

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.

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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
T1190Exploit Public-Facing Application

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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