Is CVE-2021-31755 in the CISA KEV catalog?

Yes. CVE-2021-31755 is on the CISA Known Exploited Vulnerabilities list, added 2021-11-03.

What is the CVSS severity of CVE-2021-31755?

CVE-2021-31755 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2021-31755?

CVE-2021-31755 has an EPSS score of 85.85% (100th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix or mitigate CVE-2021-31755?

No published fix for CVE-2021-31755 has been found yet. It is on the CISA Known Exploited Vulnerabilities list; federal agencies must remediate by 2021-11-17. Apply the vendor's mitigations per CISA's guidance.

CVE & CISA-KEV Catalog

CVE-2021-31755

CRITICALCISA KEVEPSS 100th pctl

9.8

CVSS v3

NVD

Description

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.

CWE-787Out-of-bounds Write

How to fix

Actively exploited, no published fix found yet

CISA required action: Apply updates per vendor instructions.

Federal remediation due: 2021-11-17

Mitigation guidance may be in the linked vendor advisories in the References section below.

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CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

85.85%probability of exploitation in 30 days

100thpercentile

Very high risk: more likely to be exploited than 100% of all known CVEs.

Known Exploited Vulnerability (CISA KEV)

Tenda AC11 Router Stack Buffer Overflow Vulnerability

Tenda AC11 devices contain a stack buffer overflow vulnerability in /goform/setmac which allows attackers to execute code via a crafted post request.

Apply updates per vendor instructions.

Remediation due: 2021-11-17

References

Exploit1

github.com

Government Resource1

cisa.gov

Related Vulnerabilities

Other CWE-787 (Out-of-bounds Write) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-22457	Critical	9.0	100%	KEV + Ransom	Fix
CVE-2025-0282	Critical	9.0	100%	KEV + Ransom	-
CVE-2015-3113	Critical	9.8	100%	KEV	Fix
CVE-2021-20038	Critical	9.8	100%	KEV + Ransom	-
CVE-2023-4863	High	8.8	100%	KEV	Fix
CVE-2020-16040	Medium	6.5	100%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-11-10.