CVE-2021-39509

Name: CVE-2021-39509
Creator: NVD / NIST
Published: 2021-08-24T19:15:32.967+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 5.10%

Last modified Jun 17, 2026

CVE-2021-39509 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. An issue was discovered in D-Link DIR-816 DIR-816A2_FWv1.10CNB05_R1B011D88210 The HTTP request parameter is used in the handler function of /goform/form2userconfig.cgi route, which can construct the user name string to delete the user function. This can lead to command injection through shell metacharacters.. EPSS estimates a 5.10% chance of exploitation in the next 30 days.

Description

An issue was discovered in D-Link DIR-816 DIR-816A2_FWv1.10CNB05_R1B011D88210 The HTTP request parameter is used in the handler function of /goform/form2userconfig.cgi route, which can construct the user name string to delete the user function. This can lead to command injection through shell metacharacters.

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

5.10%

91.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-77

Affected Software

Vendor	Product	Versions
Dlink	Dir-816 Firmware	1.10cnb05_r1b011d88210

References

https://github.com/doudoudedi/main-DIR-816_A2_Command-injectionThird Party Advisory
https://github.com/doudoudedi/main-DIR-816_A2_Command-injection/blob/main/injection.mdExploit, Third Party Advisory
https://www.dlink.com/en/security-bulletin/Vendor Advisory
https://github.com/doudoudedi/main-DIR-816_A2_Command-injectionThird Party Advisory
https://github.com/doudoudedi/main-DIR-816_A2_Command-injection/blob/main/injection.mdExploit, Third Party Advisory
https://www.dlink.com/en/security-bulletin/Vendor Advisory

Timeline

Published: Aug 24, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-39509?

How severe is CVE-2021-39509?

CVE-2021-39509 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 5.10% probability of exploitation in the next 30 days.

How do I fix CVE-2021-39509?

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-2021-39509?

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

Scan your code now

Source: NVD / NIST