CVE-2021-31755

CRITICALNVD 9.89.8—
EchelonGraph scoreHIGH confidence

Score elevated to 9.8 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 9.8 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, ghsa, nvd
Trending — 3 sources updated this weekExploited in the wild
9.8EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS PROB: 87%CVSS: 9.8Exploit: cisa kev · ssvc active · epss top5pct · epss high · public exploitExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
9.8
EG Score
9.8CRITICALhigh confidence
EG Risk
99
EG Risk 99/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation100% × 40%
Automatability100% × 15%
CISA SSVC: Attend at low mission impact; Act at medium or high.
Action: A fix is available. Apply it sooner than your standard update timelines at low mission impact and as soon as possible at medium or high.
EPSS PROB
87%
EPSS %ILE
99th
KEV
⚠ Exploited

CISA SSVCAttend at low mission impact; Act at medium or high.

A fix is available. Apply it sooner than your standard update timelines at low mission impact and as soon as possible at medium or high.

Exploitation active (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

May 7, 2021

Last Modified

November 10, 2025

Advisory Details (1)

Auto-updated Oct 1, 2026
⚠️ Active exploitation confirmed. Patch available. Sources: cisa.
cisa Patch Available🔴 Active Exploitation

Known Exploited Vulnerabilities Catalog | CISA

Known Exploited Vulnerabilities Catalog | CISA. Listed in CISA Known Exploited Vulnerabilities catalog.

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31755

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 48× in last 7d / 227× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 939 total refreshes for this CVE.

  1. 2026-10-05 15:58 UTCGHSA enrichment
  2. 2026-10-05 12:07 UTCGHSA enrichment
  3. 2026-10-05 08:16 UTCGHSA enrichment
  4. 2026-10-05 04:24 UTCGHSA enrichment
  5. 2026-10-05 00:32 UTCGHSA enrichment
  6. 2026-10-04 20:41 UTCGHSA enrichment
  7. 2026-10-04 16:49 UTCGHSA enrichment
  8. 2026-10-04 12:55 UTCGHSA enrichment
  9. 2026-10-04 09:03 UTCGHSA enrichment
  10. 2026-10-04 05:12 UTCGHSA enrichment
  11. 2026-10-04 01:20 UTCGHSA enrichment
  12. 2026-10-03 21:29 UTCGHSA enrichment
  13. 2026-10-03 17:37 UTCGHSA enrichment
  14. 2026-10-03 13:46 UTCGHSA enrichment
  15. 2026-10-03 09:53 UTCGHSA enrichment
  16. 2026-10-03 05:58 UTCGHSA enrichment
  17. 2026-10-03 02:06 UTCGHSA enrichment
  18. 2026-10-02 22:14 UTCGHSA enrichment
  19. 2026-10-02 18:23 UTCEG score recompute
  20. 2026-10-02 18:23 UTCGHSA enrichment
  21. 2026-10-02 18:23 UTCGHSA enrichment
  22. 2026-10-02 14:31 UTCGHSA enrichment
  23. 2026-10-02 10:38 UTCGHSA enrichment
  24. 2026-10-02 06:40 UTCGHSA enrichment
  25. 2026-10-02 02:47 UTCGHSA enrichment
Show 75 more
  1. 2026-10-01 22:52 UTCGHSA enrichment
  2. 2026-10-01 19:01 UTCGHSA enrichment
  3. 2026-10-01 15:09 UTCGHSA enrichment
  4. 2026-10-01 11:17 UTCGHSA enrichment
  5. 2026-10-01 07:26 UTCGHSA enrichment
  6. 2026-10-01 03:34 UTCGHSA enrichment
  7. 2026-09-30 23:42 UTCGHSA enrichment
  8. 2026-09-30 19:50 UTCGHSA enrichment
  9. 2026-09-30 15:59 UTCEG score recompute
  10. 2026-09-30 15:59 UTCGHSA enrichment
  11. 2026-09-30 15:00 UTCEPSS rescore
  12. 2026-09-30 12:07 UTCGHSA enrichment
  13. 2026-09-30 08:16 UTCGHSA enrichment
  14. 2026-09-30 04:24 UTCGHSA enrichment
  15. 2026-09-30 00:31 UTCGHSA enrichment
  16. 2026-09-29 20:39 UTCGHSA enrichment
  17. 2026-09-29 16:45 UTCGHSA enrichment
  18. 2026-09-29 12:51 UTCGHSA enrichment
  19. 2026-09-29 08:57 UTCGHSA enrichment
  20. 2026-09-29 05:05 UTCGHSA enrichment
  21. 2026-09-29 01:14 UTCEG score recompute
  22. 2026-09-29 01:14 UTCGHSA enrichment
  23. 2026-09-28 21:23 UTCGHSA enrichment
  24. 2026-09-28 17:31 UTCGHSA enrichment
  25. 2026-09-28 13:37 UTCGHSA enrichment
  26. 2026-09-28 09:46 UTCGHSA enrichment
  27. 2026-09-28 05:54 UTCGHSA enrichment
  28. 2026-09-28 02:03 UTCGHSA enrichment
  29. 2026-09-27 22:11 UTCGHSA enrichment
  30. 2026-09-27 21:51 UTCCISA KEV update
  31. 2026-09-27 18:19 UTCGHSA enrichment
  32. 2026-09-27 14:27 UTCGHSA enrichment
  33. 2026-09-27 10:36 UTCGHSA enrichment
  34. 2026-09-27 06:40 UTCGHSA enrichment
  35. 2026-09-27 02:48 UTCGHSA enrichment
  36. 2026-09-26 22:56 UTCGHSA enrichment
  37. 2026-09-26 19:04 UTCGHSA enrichment
  38. 2026-09-26 15:11 UTCGHSA enrichment
  39. 2026-09-26 11:19 UTCGHSA enrichment
  40. 2026-09-26 07:27 UTCGHSA enrichment
  41. 2026-09-26 03:33 UTCGHSA enrichment
  42. 2026-09-25 23:41 UTCGHSA enrichment
  43. 2026-09-25 19:49 UTCGHSA enrichment
  44. 2026-09-25 19:35 UTCCISA KEV update
  45. 2026-09-25 15:57 UTCGHSA enrichment
  46. 2026-09-25 14:55 UTCCISA KEV update
  47. 2026-09-25 12:06 UTCGHSA enrichment
  48. 2026-09-25 08:14 UTCGHSA enrichment
  49. 2026-09-25 04:23 UTCGHSA enrichment
  50. 2026-09-25 00:32 UTCGHSA enrichment
  51. 2026-09-24 20:40 UTCGHSA enrichment
  52. 2026-09-24 19:31 UTCCISA KEV update
  53. 2026-09-24 16:48 UTCEG score recompute
  54. 2026-09-24 16:48 UTCGHSA enrichment
  55. 2026-09-24 14:00 UTCEPSS rescore
  56. 2026-09-24 12:56 UTCGHSA enrichment
  57. 2026-09-24 09:04 UTCGHSA enrichment
  58. 2026-09-24 05:13 UTCGHSA enrichment
  59. 2026-09-24 01:21 UTCGHSA enrichment
  60. 2026-09-23 21:30 UTCGHSA enrichment
  61. 2026-09-23 17:39 UTCGHSA enrichment
  62. 2026-09-23 13:46 UTCGHSA enrichment
  63. 2026-09-23 09:55 UTCGHSA enrichment
  64. 2026-09-23 06:04 UTCGHSA enrichment
  65. 2026-09-23 02:12 UTCGHSA enrichment
  66. 2026-09-22 22:20 UTCGHSA enrichment
  67. 2026-09-22 19:36 UTCCISA KEV update
  68. 2026-09-22 18:28 UTCEG score recompute
  69. 2026-09-22 18:28 UTCGHSA enrichment
  70. 2026-09-22 14:44 UTCEPSS rescore
  71. 2026-09-22 14:37 UTCGHSA enrichment
  72. 2026-09-22 10:45 UTCGHSA enrichment
  73. 2026-09-22 06:53 UTCGHSA enrichment
  74. 2026-09-22 03:02 UTCGHSA enrichment
  75. 2026-09-21 23:10 UTCEG score recompute

Publicly available exploits

(1 reference)

Working exploit code is in the public domain. Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Nucleihttp/cves/2021/CVE-2021-31755.yaml
    First seen Jan 1, 2021

    Tenda Router AC11 - Remote Command Injection

    Open source ↗

Related CVEs(same CWE)

Frequently asked(6)

What is CVE-2021-31755?
CVE-2021-31755 is a critical vulnerability published on May 7, 2021. 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.
When was CVE-2021-31755 disclosed?
CVE-2021-31755 was first published on May 7, 2021, with the most recent update on November 10, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-31755 actively exploited?
Yes. CISA added CVE-2021-31755 to the Known Exploited Vulnerabilities catalog on November 3, 2021, affecting Tenda AC11 Router. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate attention. A fix is available. Apply it.
What is the CVSS score of CVE-2021-31755?
CVE-2021-31755 has a CVSS v3 base score of 9.8 (NVD).
Which products are affected by CVE-2021-31755?
CVE-2021-31755 affects Tenda AC11 Router.
How do I remediate CVE-2021-31755?
A fix for CVE-2021-31755 is available: update to the fixed version the vendor names in its advisory.

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