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 — 4 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: 86%CVSS: 9.8Exploit: cisa kev · ssvc active · epss top5pct · epss high · public exploitExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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
9.8(high)
EG Risk
99(Act)
EG Risk 99/100SSVC: Act

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%
Action: Fix now — active exploitation, automatable, high impact.
EPSS PROB
86%
EPSS %ILE
100%
KEV
⚠ Exploited

Published

May 7, 2021

Last Modified

November 10, 2025

Advisory Details (1)

Auto-updated Aug 20, 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 58× in last 7d / 209× 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 600 total refreshes for this CVE.

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

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 ↗

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 in the National Vulnerability Database 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 patching attention.
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. The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.
How do I remediate CVE-2021-31755?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-31755, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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