How severe is CVE-2020-27721?

CVE-2020-27721 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-2020-27721 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (59th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-27721?

CVE-2020-27721 primarily affects F5 Big-ip Domain Name System. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-27721?

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-2020-27721 published?

CVE-2020-27721 was published on 2020-12-24 and last updated on 2026-06-17.

CVE-2020-27721

CVE-2020-27721 is a high-severity vulnerability in F5 Big-ip Domain Name System 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.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 4.3
EPSS exploit prediction: 1% (59th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: F5 Big-ip Domain Name System
Published: 2020-12-24
Last modified: 2026-06-17

Description

In versions 16.0.0-16.0.0.1, 15.1.0-15.1.1, 14.1.0-14.1.3, 13.1.0-13.1.3.5, 12.1.0-12.1.5.2, and 11.6.1-11.6.5.2, in a BIG-IP DNS / BIG-IP LTM GSLB deployment, under certain circumstances, the BIG-IP DNS system may stop using a BIG-IP LTM virtual server for DNS response.

Frequently asked questions

What is CVE-2020-27721?: In versions 16.0.0-16.0.0.1, 15.1.0-15.1.1, 14.1.0-14.1.3, 13.1.0-13.1.3.5, 12.1.0-12.1.5.2, and 11.6.1-11.6.5.2, in a BIG-IP DNS / BIG-IP LTM GSLB deployment, under certain circumstances, the BIG-IP DNS system may stop using a BIG-IP LTM virtual server for DNS response.
How severe is CVE-2020-27721?: CVE-2020-27721 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-2020-27721 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (59th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-27721?: CVE-2020-27721 primarily affects F5 Big-ip Domain Name System. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-27721?: 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-2020-27721 published?: CVE-2020-27721 was published on 2020-12-24 and last updated on 2026-06-17.

References

https://support.f5.com/csp/article/K52035247

Affected products (2)

cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:*

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