Security readout for executives and security teams
Plain-English summary
CVE-2026-1637 is a critical buffer overflow in Tenda AC21 firmware version 16.03.08.16. A remote attacker with required authentication may be able to compromise the device’s confidentiality, integrity, and availability. Public proof-of-concept exploit information is reported, but CISA KEV listing is not indicated in the provided sources.
Executive priority
Treat as urgent for environments using Tenda AC21 routers. Prioritize inventory, exposure reduction, and vendor remediation checks. Public exploit availability increases practical risk, even though active exploitation is not confirmed by the provided sources.
Technical view
The flaw affects /goform/AdvSetMacMtuWan, specifically the fromAdvSetMacMtuWan function, where parameter manipulation can trigger a stack-based buffer overflow. The record maps to CWE-119 and CWE-121. CVSS v2 is 9.0 with network access, low complexity, single authentication, and complete CIA impact.
Likely exposure
Organizations using Tenda AC21 devices running firmware 16.03.08.16 are potentially exposed, especially if router administration is reachable from untrusted networks. Exposure depends on management interface accessibility and whether authentication can be obtained or bypassed by other weaknesses.
Exploitation context
The source bundle states remote exploitation is possible and that an exploit is publicly available. The CVSS vector indicates authentication is required. No provided source confirms active exploitation in the wild, and the CVE is not marked as KEV in the bundle.
Researcher notes
Evidence is primarily from the CVE record and VulDB. The GitHub reference is tagged as exploit and broken-link in the bundle, so rely cautiously on it. Sources do not provide a named fixed firmware version or confirmed vendor patch.
Mitigation direction
- Identify Tenda AC21 devices and firmware versions in use.
- Restrict router administration access to trusted management networks only.
- Disable remote management if it is not required.
- Review Tenda guidance for firmware updates or vendor mitigations.
- Replace affected devices if no supported remediation is available.
Validation and detection
- Confirm whether any AC21 device runs firmware 16.03.08.16.
- Verify management interfaces are not internet-exposed.
- Check access controls for administrative router functions.
- Monitor vendor and CVE sources for updated remediation details.
- Review logs for suspicious administrative changes or crashes.
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-119: 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-121: 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 lookupCVE-2026-1637 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
- Critical
- CVSS
- 9 (2.0)
- Known Exploited
- No
- Published
Vector: AV:N/AC:L/Au:S/C:C/I:C/A:C/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:C/I:C/A:C/E:POC/RL:ND/RC:UR810Primary CVE scoreVulnerability scoring details
Base CVSS 2.0 score
9CriticalVector: AV:N/AC:L/Au:S/C:C/I:C/A:C/E:POC/RL:ND/RC:UR
Source materials
- CVE List V5 sourceCVE List V5
- VDB-343416 | Tenda AC21 AdvSetMacMtuWan fromAdvSetMacMtuWan stack-based overflowCVE reference · vdb-entry, technical-description
- VDB-343416 | CTI Indicators (IOB, IOC, IOA)CVE reference · signature, permissions-required
- Submit #740865 | Tenda AC21 V16.03.08.16 Buffer OverflowCVE reference · third-party-advisory
- https://github.com/LX-LX88/cve/issues/25CVE 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.