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CVE-2021-27691 (GCVE-0-2021-27691)

Vulnerability from cvelistv5 – Published: 2021-04-15 23:14 – Updated: 2024-08-03 21:26
VLAI Shadowserver Previdian
Summary
Command Injection in Tenda G0 routers with firmware versions v15.11.0.6(9039)_CN and v15.11.0.5(5876)_CN , and Tenda G1 and G3 routers with firmware versions v15.11.0.17(9502)_CN or v15.11.0.16(9024)_CN allows remote attackers to execute arbitrary OS commands via a crafted action/setDebugCfg request. This occurs because the "formSetDebugCfg" function executes glibc's system function with untrusted input.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE
  • n/a
Assigner
References
Shadowserver
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 0c8bcb61-ef5d-4db5-84dc-240ff667d2c3

Vulnerability ID: CVE-2021-27691

Status: Confirmed

Status Updated: 2026-09-07 00:00 UTC

Exploited: Yes

Characteristics
Severity: 98.0
Timestamps
First Seen: 2026-08-22
Asserted: 2026-08-22
Last Seen: 2026-09-07
Scope
Asset Exposure: ['internet-facing']
Notes: Affected: Tenda / Tenda G0/G1/G3 | Class: router | Severity: Critical (CVSS 9.8) | IoT: no | In CISA KEV: no | Honeypot connections on 2026-09-07: 18
Evidence

Type: Honeypot

Signal: In The Wild Attempts

Confidence: 70%

Source: shadowserver

Details
1D 8
Iot no
Feed Shadowserver Foundation honeypot/exploited-vulnerabilities
Type http-scan
Class router
7D Avg 15
Vendor Tenda
30D Avg 50
90D Avg 16
Product Tenda G0/G1/G3
Cisa Kev no
Connections 18
Observation Date 2026-09-07
Vulnerability Class CVSS
Vulnerability Score 9.8
Vulnerability Severity Critical
References
Created: 2026-08-24 01:00 UTC | Updated: 2026-09-09 01:00 UTC
Previdian
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 39ee7ca1-fe23-494e-8a9e-ae5f349620a0

Vulnerability ID: CVE-2021-27691

Status: Confirmed

Status Updated: 2026-08-22 00:00 UTC

Exploited: Yes

Timestamps
First Seen: 2026-08-22
Asserted: 2026-08-22
Scope
Notes: Command Injection in Tenda G0 routers with firmware versions v15.11.0.6(9039)_CN and v15.11.0.5(5876)_CN , and Tenda G1 and G3 routers with... | Affected: Tenda / G0, G1, G3 routers | CVSS: 9.8 (CRITICAL) | EPSS: 0.25183 | Used in malware: unknown | Not yet in CISA KEV: True
Evidence

Type: Public Report

Signal: Successful Exploitation

Confidence: 70%

Source: kevintel

Details
Feed KEVIntel (kevintel.com)
Title Command Injection in Tenda G0 routers with firmware versions v15.11.0.6(9039)_CN and v15.11.0.5(5876)_CN , and Tenda G1 and G3 routers with...
Vendor Tenda
Product G0, G1, G3 routers
Added Date 2026-08-22T00:00:00.000Z
Cvss Score 9.8
Epss Score 0.25183
Cvss Severity CRITICAL
Epss Percentile 0.97767
Used In Malware unknown
Ahead Of Cisa Kev None
Not Yet In Cisa Kev True
References
Created: 2026-08-23 11:00 UTC | Updated: 2026-08-23 11:00 UTC
Show details on NVD website
To clipboard 

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    "redhat_vex": {
      "current_release_date": "2026-03-27T14:24:03+00:00",
      "cve": "CVE-2021-27691",
      "id": "CVE-2021-27691",
      "initial_release_date": "2021-01-01T00:00:00+00:00",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "CVE-2021-27691",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-27691.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.