ExploitedNot in CISA KEV yet

CVE-2021-27691

Exploitation confirmed. First attested on 2026-08-22 by GCVE · kevintel, GCVE · shadowserver.

Published2021-04-16
WeaknessCWE-119 · CWE-78

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC

2021-04-1600:15CVE publishedNVD
2026-08-22Listed as exploited by GCVEGCVE
2026-08-22Exploitation first reportedGCVE
2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-27691?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-27691?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Tendacn g0 firmwareversion to verify

Branch	Affected	Fixed in	Source
15.11	= 15.11.0.5\(5876\)_cn	no fix published	NVD
15.11	= 15.11.0.6\(9039\)_cn	no fix published	NVD

Tendacn g1 firmwareversion to verify

Branch	Affected	Fixed in	Source
15.11	= 15.11.0.16\(9024\)_cn	no fix published	NVD
15.11	= 15.11.0.17\(9502\)_cn	no fix published	NVD

Tendacn g3 firmwareversion to verify

Branch	Affected	Fixed in	Source
15.11	= 15.11.0.16\(9024\)_cn	no fix published	NVD
15.11	= 15.11.0.17\(9502\)_cn	no fix published	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

No fix published by the sources we read yet. NVD record

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

GCVEexploitation2026-08-22
NVDCVSS 3.19.8read 2026-10-23
NVDCVSS 2.010read 2026-10-23
NVDweakness (CWE)CWE-119, CWE-78read 2026-10-23
FIRST EPSSEPSS score25.4 %read 2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: 2021-04-16
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-27691?

Is CVE-2021-27691 actively exploited?

Active exploitation of CVE-2021-27691 has not been confirmed. Its EPSS score was 25.4% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-27691?

CVE-2021-27691 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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