CVE-2021-27565

Name: CVE-2021-27565
Creator: NVD / NIST
Published: 2021-08-19T12:15:08.627+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 2.59%

Last modified Jun 17, 2026

CVE-2021-27565 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. The web server in InterNiche NicheStack through 4.0.1 allows remote attackers to cause a denial of service (infinite loop and networking outage) via an unexpected valid HTTP request such as OPTIONS. This occurs because the HTTP request handler enters a miscoded wbs_loop() debugger hook.. EPSS estimates a 2.59% chance of exploitation in the next 30 days.

Description

The web server in InterNiche NicheStack through 4.0.1 allows remote attackers to cause a denial of service (infinite loop and networking outage) via an unexpected valid HTTP request such as OPTIONS. This occurs because the HTTP request handler enters a miscoded wbs_loop() debugger hook.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

2.59%

83.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-835

Affected Software

Vendor	Product	Versions
Hcc-Embedded	Nichestack	<= 4.0.1

References

https://www.forescout.com/blog/new-critical-operational-technology-vulnerabilities-found-on-nichestack/Mitigation, Third Party Advisory
https://www.hcc-embedded.com/Product
https://www.hcc-embedded.com/about/about-internicheProduct
https://www.kb.cert.org/vuls/id/608209Third Party Advisory, US Government Resource
https://www.forescout.com/blog/new-critical-operational-technology-vulnerabilities-found-on-nichestack/Mitigation, Third Party Advisory
https://www.hcc-embedded.com/Product
https://www.hcc-embedded.com/about/about-internicheProduct
https://www.kb.cert.org/vuls/id/608209Third Party Advisory, US Government Resource

Timeline

Published: Aug 19, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-27565?

How severe is CVE-2021-27565?

CVE-2021-27565 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 2.59% probability of exploitation in the next 30 days.

How do I fix CVE-2021-27565?

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-2021-27565?

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

Scan your code now

Source: NVD / NIST