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ExploitedIn CISA KEV

CVE-2021-31755

Exploitation confirmed. First attested on 2021-11-03 by CISA-ADP, CISA KEV, GCVE · kevintel, GCVE · shadowserver.

  • Published2021-05-07
  • WeaknessCWE-787

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2021-05-0723:15CVE publishedNVD
  2. 2021-11-03Added to the CISA KEV catalogCISA KEV
  3. 2021-11-03Listed as exploited by GCVEGCVE
  4. 2021-11-03Exploitation first reportedCISA KEV
  5. 2025-02-0419:44SSVC exploitation set to activeCISA-ADP

Observed activity

isMalicious corpus · updated 2026-11-03 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-31755?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-31755?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Tenda ac11 firmwareversion to verify
BranchAffectedFixed in
2.3≤ 02.03.01.104_cnno fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. CISA’s required action: Apply updates per vendor instructions.due 2021-11-17

Detection

read 2026-11-03 22:42 UTC
Nuclei template
available
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

CISA Known Exploited Vulnerability

Date Added
2021-11-03
Patch Due Date
2021-11-17
Ransomware Use
Unknown
Required Action
Apply updates per vendor instructions.

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2021-05-07
Last Modified
2026-06-17
NVD status
Analyzed
GitHub Advisory
GHSA-539c-2w6v-9rwx

Frequently asked questions

What is CVE-2021-31755?

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.

Is CVE-2021-31755 actively exploited?

Yes. CVE-2021-31755 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, meaning it has been confirmed as actively exploited in the wild. CISA requires federal agencies to patch by 2021-11-17.

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

CVE-2021-31755 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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Sources for this record