Security readout for executives and security teams
Plain-English summary
Tenda AC11 routers running firmware through 02.03.01.104_CN have a critical memory corruption flaw that can allow unauthenticated remote code execution. For executives, the business issue is simple: exposed vulnerable routers can become attacker-controlled infrastructure.
Executive priority
Prioritize urgently if any Tenda AC11 devices exist in business networks. KEV status and unauthenticated remote code execution make this a high-risk edge-device issue, especially for internet-facing deployments.
Technical view
CVE-2021-31755 is a CWE-787 stack buffer overflow in /goform/setmac on Tenda AC11 firmware through 02.03.01.104_CN. The CVSS 3.1 score is 9.8, with network access, low complexity, no privileges, and no user interaction required.
Likely exposure
Exposure is likely where Tenda AC11 devices are deployed and their management or affected web interface is reachable from untrusted networks. The CVE bundle’s structured affected-product fields are incomplete, so inventory confirmation is required.
Exploitation context
CISA lists CVE-2021-31755 in the Known Exploited Vulnerabilities catalog, which supports known exploitation. The provided sources do not describe campaign details, exploitation scale, target sectors, or current attacker tooling.
Researcher notes
Evidence supports a stack buffer overflow in /goform/setmac with arbitrary code execution impact. Public source detail is limited in this bundle, and vendor remediation specifics are not provided, so avoid assuming a patch version without vendor confirmation.
Mitigation direction
- Identify Tenda AC11 devices and firmware versions in asset inventory.
- Check Tenda or device-provider guidance for fixed firmware or replacement advice.
- Remove management access from the internet and untrusted networks.
- Segment affected routers from sensitive internal systems.
- Replace unsupported devices if no trusted fixed firmware is available.
Validation and detection
- Confirm whether any Tenda AC11 runs firmware through 02.03.01.104_CN.
- Verify the affected web interface is not reachable externally.
- Review firewall and remote-management exposure for these devices.
- Check logs for unexpected administrative changes or unusual router activity.
- Document remediation status for KEV-driven vulnerability management tracking.
Public sources used
Michael Williams reviewed this cited source version on .
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
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CWE-787: Exact CWE lookup
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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-2021-31755 mapping review
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Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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.
CISA KEV status
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/Yu3H0/IoT_CVE/tree/main/Tenda/CVE_3CVE reference · x_refsource_MISC
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31755CVE reference · government-resource
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.
Out-of-bounds Write
Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.