How severe is CVE-2020-27633?

CVE-2020-27633 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2020-27633 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-27633?

CVE-2020-27633 affects Butok Fnet. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-27633?

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

When was CVE-2020-27633 published?

CVE-2020-27633 was published on 2023-10-10 and last updated on 2026-06-17.

CVE-2020-27633

CVE-2020-27633 is a critical-severity vulnerability in Butok Fnet with a CVSS 3.x base score of 9.1. 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-330.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
EPSS exploit prediction: 1% (54th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-330
Affected product: Butok Fnet
Published: 2023-10-10
Last modified: 2026-06-17

Description

In FNET 4.6.3, TCP ISNs are improperly random.

Frequently asked questions

What is CVE-2020-27633?: In FNET 4.6.3, TCP ISNs are improperly random.
How severe is CVE-2020-27633?: CVE-2020-27633 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2020-27633 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-27633?: CVE-2020-27633 affects Butok Fnet. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-27633?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2020-27633 published?: CVE-2020-27633 was published on 2023-10-10 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:butok:fnet:4.6.3:*:*:*:*:*:*:*

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