CVE-2021-27691

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.

Published: 2021-04-15 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-27691 is rated High Risk (78.4/100): CVSS Critical severity, with high exploitation likelihood (EPSS 25.18%, 98th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. EPSS rose +20.79% over the last day, indicating growing attacker interest. High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-27691

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 4.40% 25.18% +20.79%
2 2025-11-21 3.36% 4.40% +1.04%
3 2025-11-18 — 3.36% —

Full EPSS history (15 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-27691

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
10.0 2.0 HIGH
AV:N/AC:L/Au:N/C:C/I:C/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 10.0 10.0 [email protected]

Weakness enumeration for CVE-2021-27691

Affected software / configurations for CVE-2021-27691

Vendor Product Version Raw CPE
tendacn g0_firmware 15.11.0.5\(5876\)_cn cpe:2.3:o:tendacn:g0_firmware:15.11.0.5\(5876\)_cn:*:*:*:*:*:*:*
tendacn g0_firmware 15.11.0.6\(9039\)_cn cpe:2.3:o:tendacn:g0_firmware:15.11.0.6\(9039\)_cn:*:*:*:*:*:*:*
tendacn g1_firmware 15.11.0.16\(9024\)_cn cpe:2.3:o:tendacn:g1_firmware:15.11.0.16\(9024\)_cn:*:*:*:*:*:*:*
tendacn g1_firmware 15.11.0.17\(9502\)_cn cpe:2.3:o:tendacn:g1_firmware:15.11.0.17\(9502\)_cn:*:*:*:*:*:*:*
tendacn g3_firmware 15.11.0.16\(9024\)_cn cpe:2.3:o:tendacn:g3_firmware:15.11.0.16\(9024\)_cn:*:*:*:*:*:*:*
tendacn g3_firmware 15.11.0.17\(9502\)_cn cpe:2.3:o:tendacn:g3_firmware:15.11.0.17\(9502\)_cn:*:*:*:*:*:*:*

References for CVE-2021-27691

cvelogic Threat Intelligence