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CVE-2021-31755· NVD / CVE Program· CNA mitre

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 /goform/setmac allows attackers to execute arbitrary code on the system via a crafted post request.

CriticalCVSS 9.8 · v3.1KEVWeaponized No fix recorded
Published
May 7, 2021
Updated
Jun 16, 2026
EPSS
86.9% · 100th percentile
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Action score

95

Now

Patch today or shut off access.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
30 / 30 · Listed
EPSS
26 / 30 · 86.9%

CISA SSVC decision

Exploitation
active
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

Actively exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on Nov 3, 2021. That signals real attacks, not theory.

Remediation deadline for government agencies: Nov 17, 2021.

Affected systems

VendorProduct
tendaac11 firmware
tendaac11

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • tenda ac11 firmwareup to 02.03.01.104_cn inclusive

Same product

tenda: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-31758An issue was discovered on Tenda AC11 devices with firmware through 02.03.01.104_CN.
    41Plan
  • CVE-2021-46321Tenda AC Series Router AC11_V02.03.01.104_CN was discovered to contain a stack buffer overflow in the wifiBasicCfg module.
    40Plan
  • CVE-2021-46265Tenda AC Series Router AC11_V02.03.01.104_CN was discovered to contain a stack buffer overflow in the wanBasicCfg module.
    40Plan
  • CVE-2021-46264Tenda AC Series Router AC11_V02.03.01.104_CN was discovered to contain a stack buffer overflow in the onlineList module.
    40Plan
  • CVE-2021-46263Tenda AC Series Router AC11_V02.03.01.104_CN was discovered to contain a stack buffer overflow in the wifiTime module.
    40Plan
  • CVE-2021-46262Tenda AC Series Router AC11_V02.03.01.104_CN was discovered to contain a stack buffer overflow in the PPPoE module.
    40Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Evidence

  • Nuclei detection template ×1

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Nuclei detection templateNuclei template CVE-2021-31755 —

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. CISA KEV+179 d
  3. TodaySep 29, 2026+1971 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-787 · Out-of-bounds Write

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records