How severe is CVE-2023-20027?

CVE-2023-20027 has a CVSS 3.x base score of 8.6, 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-2023-20027 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-20027?

CVE-2023-20027 primarily affects Cisco Ios Xe. In total, 190 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2023-20027?

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-2023-20027 published?

CVE-2023-20027 was published on 2023-03-23 and last updated on 2026-06-17.

CVE-2023-20027

CVE-2023-20027 is a high-severity vulnerability in Cisco Ios Xe with a CVSS 3.x base score of 8.6. 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-416.

Key facts

Severity: High (CVSS 3.x base score 8.6)
EPSS exploit prediction: 1% (58th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-416
Affected product: Cisco Ios Xe
Published: 2023-03-23
Last modified: 2026-06-17

Description

A vulnerability in the implementation of the IPv4 Virtual Fragmentation Reassembly (VFR) feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper reassembly of large packets that occurs when VFR is enabled on either a tunnel interface or on a physical interface that is configured with a maximum transmission unit (MTU) greater than 4,615 bytes. An attacker could exploit this vulnerability by sending fragmented packets through a VFR-enabled interface on an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

Frequently asked questions

What is CVE-2023-20027?: A vulnerability in the implementation of the IPv4 Virtual Fragmentation Reassembly (VFR) feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper reassembly of large packets that occurs when VFR is enabled on either a tunnel interface or on a physical interface that is configured with a maximum transmission unit (MTU) greater than 4,615 bytes. An attacker could exploit this vulnerability by sending fragmented packets through a VFR-enabled interface on an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.
How severe is CVE-2023-20027?: CVE-2023-20027 has a CVSS 3.x base score of 8.6, 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-2023-20027 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-20027?: CVE-2023-20027 primarily affects Cisco Ios Xe. In total, 190 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2023-20027?: 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-2023-20027 published?: CVE-2023-20027 was published on 2023-03-23 and last updated on 2026-06-17.

References

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ipv4-vfr-dos-CXxtFacb

Affected products (190)

cpe:2.3:o:cisco:ios_xe:3.9.0as:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.9.1s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.9.2s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.0s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.1s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.2as:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.2s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.2ts:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.3s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.4s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.5s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.6s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.7s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.8as:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.8s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.9s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.10.10s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.11.0s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.11.1s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.11.2s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.11.3s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.11.4s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.12.0s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.12.1s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.12.2s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.12.3s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.12.4s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.13.0s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.13.1s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.13.2s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.13.3s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.13.4s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.13.5s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.13.6as:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.13.6s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.13.7s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.13.8s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.13.9s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.13.10s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.14.0s:*:*:*:*:*:*:*

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