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CVE Record

CVE-2021-31756: An issue was discovered on Tenda AC11 devices with firmware through 02.03.01.104_CN.

An issue was discovered on Tenda AC11 devices with firmware through 02.03.01.104_CN. A stack buffer overflow vulnerability in /gofrom/setwanType allows attackers to execute arbitrary code on the system via a crafted post request. This occurs when input vector controlled by malicious attack get copied to the stack variable.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2021-31756 is a reported memory-safety flaw in Tenda AC11 routers running firmware through 02.03.01.104_CN. A malicious request to a WAN-type configuration endpoint may let an attacker run code on the device. Public sources do not provide CVSS, a named patch, or evidence of active exploitation.

Executive priority

Treat this as a high-priority edge-device risk if Tenda AC11 routers are present. The business urgency depends on exposure: internet-reachable administration sharply increases concern. If no vendor fix exists, replacement or isolation may be the practical control.

Technical view

The CVE describes a stack buffer overflow in /gofrom/setwanType on Tenda AC11 firmware through 02.03.01.104_CN. Attacker-controlled input is copied into a stack variable, creating possible arbitrary code execution. The record has no CVSS, CWE, CPE, or vendor remediation details in the supplied sources.

Likely exposure

Exposure is likely limited to organizations or sites using Tenda AC11 devices on firmware through 02.03.01.104_CN, especially where router management or related endpoints are reachable from untrusted networks.

Exploitation context

The source bundle states arbitrary code execution may be possible via a crafted POST request. CISA KEV status is false, and the supplied sources do not establish active exploitation in the wild.

Researcher notes

Evidence is sparse: the CVE record names the endpoint, affected firmware ceiling, and stack overflow behavior, but lacks CVSS, CPEs, CWE mapping, and remediation. Avoid assuming broader Tenda models or other firmware branches are affected without vendor or researcher confirmation.

Mitigation direction

  • Inventory Tenda AC11 routers and record firmware versions.
  • Check Tenda support channels for fixed firmware or replacement guidance.
  • Disable WAN-side or untrusted access to router management interfaces.
  • Restrict administration to trusted networks or VPN access only.
  • Replace affected devices if no supported fixed firmware is available.

Validation and detection

  • Confirm whether any Tenda AC11 devices run firmware through 02.03.01.104_CN.
  • Review network exposure of router management interfaces and configuration endpoints.
  • Verify remote administration is disabled or restricted to trusted sources.
  • Review router logs for unexpected administration or configuration changes.
  • Document vendor guidance found before applying firmware or replacement actions.
Prepared
Confidence
medium
Sources
3

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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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description · low confidence lookup

Execution 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.

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CVE-2021-31756 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

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.

0CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.