CVE-2021-27691G0 Firmware OS Command Injection
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…
Published Apr 15, 2021 · Updated Nov 21, 2024
Key Facts
Patch immediately- CVE-2021-27691 is a critical-severity vulnerability (CVSS 9.8 v3.1) affecting G0 Firmware (Tendacn), G1 Firmware (Tendacn), G3 Firmware (Tendacn).
- It is exploited in the wild, listed in CIRCL KEV, Industry KEV feed since Aug 22, 2026. No public exploit code is known.
- EPSS estimates a 25% probability of exploitation in the next 30 days.
- No fixed version is listed yet; check the vendor advisory for mitigations.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
Scores
CVSS v3.1
9.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
25%
Higher than 97.9% of all scored CVEs
Exploit maturity
Exploited (KEV)
ATLAS score
48/100
Publication score, see How it works
Exploitation Verdict
KEV listed
Aug 22, 2026
1955 days after publication
Federal due date
None
No federal due date
Ransomware use
Not reported
Attributed actors
None named
Exploit & Defence Guidance
Exploit maturity
Exploited (KEV)
Public exploit code
0
Proof-of-concept links
In-the-wild evidence
10
Reports of active use
Description
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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CIRCL KEV | Aug 22, 2026 | n/a | Not reported |
| Industry KEV feed | Aug 22, 2026 | n/a | Not reported |
Affected Products
6 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| G0 FirmwareTendacn | 15.11.0.5\(5876\)_cn, 15.11.0.6\(9039\)_cn | n/a |
| G1 FirmwareTendacn | 15.11.0.16\(9024\)_cn, 15.11.0.17\(9502\)_cn | n/a |
| G3 FirmwareTendacn | 15.11.0.16\(9024\)_cn, 15.11.0.17\(9502\)_cn | n/a |
Timeline
Publicly disclosed
Apr 15, 2021
Last updated
Nov 21, 2024
Added to CIRCL KEV
Aug 22, 2026
Added to Industry KEV feed
Aug 22, 2026
Weakness Type
- CWE-78 Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
- CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer
References
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
FAQ
Common Questions.
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.
Affected: G0 Firmware (Tendacn) versions 15.11.0.5\(5876\)_cn, 15.11.0.6\(9039\)_cn; G1 Firmware (Tendacn) versions 15.11.0.16\(9024\)_cn, 15.11.0.17\(9502\)_cn; G3 Firmware (Tendacn) versions 15.11.0.16\(9024\)_cn, 15.11.0.17\(9502\)_cn. The full list is in the CVE brief.
It is exploited in the wild, listed in CIRCL KEV, Industry KEV feed since Aug 22, 2026.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
No fixed version is listed yet; check the vendor advisory for mitigations.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
Is CVE-2021-27691 On Your Attack Surface?
Brandefense matches it against the products discovered on your perimeter and opens a finding the day a CVE like this is listed.
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