Security readout for executives and security teams
Plain-English summary
CVE-2026-1638 is a command injection flaw in Tenda AC21 router firmware. A remote authenticated attacker could abuse the DMZ configuration function to run system commands on the device. Public exploit information is reported, but the provided sources do not show CISA KEV listing or confirmed active exploitation.
Executive priority
Prioritize if Tenda AC21 routers are internet-managed, used in business networks, or rely on weak administrator controls. The issue is not confirmed as actively exploited, but public exploit availability and command execution impact justify timely containment and vendor follow-up.
Technical view
The flaw affects /goform/mDMZSetCfg in Tenda AC21 firmware versions listed as 1.1.1.1, 1.dmzip, and 16.03.08.16. Manipulation of the dmzIp argument can lead to command injection. VulDB rates it CVSS 2.0 6.5 with network access, low complexity, and required authentication.
Likely exposure
Exposure is most relevant where affected Tenda AC21 routers are deployed and their administrative interface is reachable by untrusted users or networks. Because authentication is required, weak, shared, or compromised router credentials increase practical risk.
Exploitation context
The source bundle states exploit material has been released publicly and may be used for attacks. However, KEV is false and no cited source confirms active exploitation. Treat internet-exposed or poorly controlled admin interfaces as higher priority.
Researcher notes
Evidence is primarily from CVE/VulDB records. The affected endpoint and parameter are identified, but the provided sources do not include an official fixed version, patch note, or confirmed exploitation telemetry. Avoid assuming broader Tenda models are affected without vendor confirmation.
Mitigation direction
- Check Tenda advisories and firmware downloads for a vendor-approved update or workaround.
- Restrict router administration access to trusted internal networks only.
- Disable remote administration if it is not required.
- Use unique, strong administrator credentials on affected devices.
- Replace affected devices if no supported firmware or mitigation is available.
Validation and detection
- Inventory Tenda AC21 devices and record firmware versions.
- Identify whether router administration is reachable from the internet or untrusted networks.
- Review configuration for DMZ features and administrative access exposure.
- Check logs for suspicious administrator logins or unexpected configuration changes.
- Track vendor guidance and retest after applying any official update.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-74: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-77: Command execution behavior lookup
Command injection weaknesses can lead defenders to review execution techniques and command interpreter telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-1638 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.5 (2.0)
- Known Exploited
- No
- Published
Vector: AV:N/AC:L/Au:S/C:P/I:P/A:P/E:POC/RL:ND/RC:UR
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
AV:N/AC:L/Au:S/C:P/I:P/A:P/E:POC/RL:ND/RC:UR86.4Primary CVE scoreVulnerability scoring details
Base CVSS 2.0 score
6.5MediumVector: AV:N/AC:L/Au:S/C:P/I:P/A:P/E:POC/RL:ND/RC:UR
Source materials
- CVE List V5 sourceCVE List V5
- VDB-343417 | Tenda AC21 mDMZSetCfg command injectionCVE reference · vdb-entry, technical-description
- VDB-343417 | CTI Indicators (IOB, IOC, TTP, IOA)CVE reference · signature, permissions-required
- Submit #740871 | Tenda AC21 V16.03.08.16 Command InjectionCVE reference · third-party-advisory
- https://github.com/LX-LX88/cve/issues/26CVE reference · broken-link, exploit
- https://www.tenda.com.cn/CVE reference · product
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.