CVE-2021-27705

Name: CVE-2021-27705
Creator: NVD / NIST
Published: 2021-04-14T15:15:13.97+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 2.94%

Last modified Jun 17, 2026

CVE-2021-27705 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. Buffer Overflow in Tenda G1 and G3 routers with firmware v15.11.0.17(9502)_CN allows remote attackers to execute arbitrary code via a crafted action/"qosIndex "request. This occurs because the "formQOSRuleDel" function directly passes the parameter "qosIndex" to strcpy without limit.. EPSS estimates a 2.94% chance of exploitation in the next 30 days.

Description

Buffer Overflow in Tenda G1 and G3 routers with firmware v15.11.0.17(9502)_CN allows remote attackers to execute arbitrary code via a crafted action/"qosIndex "request. This occurs because the "formQOSRuleDel" function directly passes the parameter "qosIndex" to strcpy without limit.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

2.94%

85.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-120

Affected Software

Vendor	Product	Versions
Tenda	G1 Firmware	v15.11.0.17\(9502\)_cn
Tenda	G3 Firmware	v15.11.0.17\(9502\)_cn

References

https://hackmd.io/Zb7lfFaNR0ScpaTssECFbgExploit, Third Party Advisory
https://hackmd.io/Zb7lfFaNR0ScpaTssECFbgExploit, Third Party Advisory

Timeline

Published: Apr 14, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-27705?

How severe is CVE-2021-27705?

CVE-2021-27705 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 2.94% probability of exploitation in the next 30 days.

How do I fix CVE-2021-27705?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-27705?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST