CVE-2026-1638
Published: 30 January 2026
Summary
CVE-2026-1638 is a medium-severity Injection (CWE-74) vulnerability in Tenda Ac21 Firmware. Its CVSS base score is 6.3 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 33.1th 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-2 (Flaw Remediation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly mitigates the command injection vulnerability by requiring validation of the dmzIp argument in the mDMZSetCfg function to block malicious payloads.
Requires timely identification, reporting, and correction of the specific command injection flaw in Tenda AC21 firmware.
Enforces restrictions on dmzIp inputs such as length and format to limit opportunities for command injection payloads.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Command injection in public-facing router web interface enables exploitation of public-facing applications (T1190) and arbitrary command execution via network device CLI (T1059.008).
NVD Description
A security flaw has been discovered in Tenda AC21 1.1.1.1/1.dmzip/16.03.08.16. The impacted element is the function mDMZSetCfg of the file /goform/mDMZSetCfg. The manipulation of the argument dmzIp results in command injection. The attack can be executed remotely. The exploit has…
more
been released to the public and may be used for attacks.
Deeper analysisAI
CVE-2026-1638 is a command injection vulnerability (CWE-74, CWE-77) affecting Tenda AC21 routers on firmware version 1.1.1.1/1.dmzip/16.03.08.16. The flaw resides in the mDMZSetCfg function within the /goform/mDMZSetCfg file, where manipulation of the dmzIp argument enables arbitrary command execution.
The vulnerability is remotely exploitable over the network (AV:N) with low attack complexity (AC:L), requiring low privileges (PR:L) and no user interaction (UI:N), with unchanged scope (S:U). Successful exploitation yields low impacts on confidentiality, integrity, and availability (C:L/I:L/A:L), for an overall CVSS v3.1 base score of 6.3. An exploit has been publicly released, enabling attacks by remote authenticated users with minimal privileges.
Advisories detail the issue on VulDB (ctiid.343417, id.343417, submit.740871) and a GitHub repository issue (LX-LX88/cve/issues/26), with the vendor site at tenda.com.cn listed as a reference. No specific patch or mitigation steps are outlined in the disclosure summary.
The public exploit release heightens the risk of real-world exploitation against unpatched Tenda AC21 devices.
Details
- CWE(s)