How severe is CVE-2021-27565?

CVE-2021-27565 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-27565 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27565?

CVE-2021-27565 affects Hcc-embedded Nichestack. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-27565?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-27565 published?

CVE-2021-27565 was published on 2021-08-19 and last updated on 2026-06-17.

CVE-2021-27565

CVE-2021-27565 is a high-severity vulnerability in Hcc-embedded Nichestack with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-835.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 3% (83rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-835
Affected product: Hcc-embedded Nichestack
Published: 2021-08-19
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-27565?: 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.
How severe is CVE-2021-27565?: CVE-2021-27565 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-27565 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27565?: CVE-2021-27565 affects Hcc-embedded Nichestack. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-27565?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-27565 published?: CVE-2021-27565 was published on 2021-08-19 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:hcc-embedded:nichestack:*:*:*:*:*:*:*:*

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