How severe is CVE-2020-3359?

CVE-2020-3359 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-2020-3359 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (71st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-3359?

CVE-2020-3359 affects Cisco Ios Xe. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-3359?

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-2020-3359 published?

CVE-2020-3359 was published on 2020-09-24 and last updated on 2026-06-17.

CVE-2020-3359

CVE-2020-3359 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-20.

Key facts

Severity: High (CVSS 3.x base score 8.6)
CVSS v2: 7.8
EPSS exploit prediction: 2% (71st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Cisco Ios Xe
Published: 2020-09-24
Last modified: 2026-06-17

Description

A vulnerability in the multicast DNS (mDNS) feature of Cisco IOS XE Software for Cisco Catalyst 9800 Series Wireless Controllers could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is due to improper validation of mDNS packets. An attacker could exploit this vulnerability by sending a crafted mDNS packet to an affected device. A successful exploit could cause a device to reload, resulting in a DoS condition.

Frequently asked questions

What is CVE-2020-3359?: A vulnerability in the multicast DNS (mDNS) feature of Cisco IOS XE Software for Cisco Catalyst 9800 Series Wireless Controllers could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is due to improper validation of mDNS packets. An attacker could exploit this vulnerability by sending a crafted mDNS packet to an affected device. A successful exploit could cause a device to reload, resulting in a DoS condition.
How severe is CVE-2020-3359?: CVE-2020-3359 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-2020-3359 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (71st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-3359?: CVE-2020-3359 affects Cisco Ios Xe. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-3359?: 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-2020-3359 published?: CVE-2020-3359 was published on 2020-09-24 and last updated on 2026-06-17.

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-mdns-dos-3tH6cA9J

Affected products (1)

cpe:2.3:o:cisco:ios_xe:16.12.1:*:*:*:*:*:*:*

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