cve recordhighexploited in the wild3 of 3 cataloguesexploit reported

CVE-2021-31755

Tenda · AC11 Router · Tenda AC11 Router Stack Buffer Overflow Vulnerability

· Added to CISA KEV Nov 3, 2021

CVSS—

Severityhigh

Weakness—

EPSS86.5%99.7th percentile

Exploited3 KEV sources

Ransomware useUnknown

Federal fix dueNov 17, 2021

patch window

Called exploited 48 days after disclosure.

Measured from the CVE publication date to the earliest of 3 KEV catalogues that list it.

The life of this vulnerability

CVE publishedMay 7, 2021
First KEV listingJun 24, 202148d
Last KEV listingNov 3, 20214mo
Last sightingSep 4, 20264.8y

Gaps are compressed to equal steps. The elapsed time is printed under each.

Which catalogues call it exploited

CISA KEVUS federallisted Nov 3, 2021
EUVDENISA, European Unionlisted Nov 3, 2021
VulnCheck KEVcommercial researchlisted Jun 24, 2021
CIRCLaggregator, mirrors the abovelisted Nov 3, 2021, not counted

Sources3 of 3

Listings differ by132 d

Strongest claimconfirmed

3 catalogues list it. CIRCL aggregates the others and is shown but not counted.

Public exploitation evidence

reported exploitationSep 4, 2026dashboard.shadowserver.org/statistics/honeypot/vulnerability
reported exploitationSep 2, 2026dashboard.shadowserver.org/statistics/honeypot/vulnerability
reported exploitationSep 1, 2026dashboard.shadowserver.org/statistics/honeypot/vulnerability
reported exploitationAug 31, 2026dashboard.shadowserver.org/statistics/honeypot/vulnerability
reported exploitationAug 30, 2026dashboard.shadowserver.org/statistics/honeypot/vulnerability
reported exploitationAug 28, 2026dashboard.shadowserver.org/statistics/honeypot/vulnerability

697 public reports collected from VulnCheck and CIRCL, first on Jun 24, 2021. Each links to its original source. We have not verified them.

Description

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

Required action (CISA)

Apply updates per vendor instructions.

References

← Back to the CVE Tracker

Our coverage of CVE-2021-31755

CVE-2008-4128Aug 7, 2026high

July 2026 CVE Landscape

Cybersecurity researchers identified 85 high-impact vulnerabilities in July 2026 that require urgent remediation, marking a 44% increase from the previous month. Of these, 36 were assigned a "Very Critical" risk score by Insikt Group. The vulnerabilities affected products from 61 vendors, with Microsoft accounting for approximately 12% of the total.