How severe is CVE-2020-3559?

CVE-2020-3559 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-2020-3559 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (69th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-3559?

CVE-2020-3559 primarily affects Cisco Wireless Lan Controller. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-3559?

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-2020-3559 published?

CVE-2020-3559 was published on 2020-09-24 and last updated on 2026-06-17.

CVE-2020-3559

CVE-2020-3559 is a high-severity vulnerability in Cisco Wireless Lan Controller 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-400.

Key facts

Severity: High (CVSS 3.x base score 8.6)
CVSS v2: 7.8
EPSS exploit prediction: 1% (69th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-400
Affected product: Cisco Wireless Lan Controller
Published: 2020-09-24
Last modified: 2026-06-17

Description

A vulnerability in Cisco Aironet Access Point (AP) Software could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to improper handling of clients that are trying to connect to the AP. An attacker could exploit this vulnerability by sending authentication requests from multiple clients to an affected device. A successful exploit could allow the attacker to cause the affected device to reload.

Frequently asked questions

What is CVE-2020-3559?: A vulnerability in Cisco Aironet Access Point (AP) Software could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to improper handling of clients that are trying to connect to the AP. An attacker could exploit this vulnerability by sending authentication requests from multiple clients to an affected device. A successful exploit could allow the attacker to cause the affected device to reload.
How severe is CVE-2020-3559?: CVE-2020-3559 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-2020-3559 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (69th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-3559?: CVE-2020-3559 primarily affects Cisco Wireless Lan Controller. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-3559?: 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-2020-3559 published?: CVE-2020-3559 was published on 2020-09-24 and last updated on 2026-06-17.

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-aironet-dos-h3DCuLXw

Affected products (5)

cpe:2.3:o:cisco:wireless_lan_controller:*:*:*:*:*:*:*:*
cpe:2.3:a:cisco:business_access_points:*:*:*:*:*:*:*:*
cpe:2.3:o:cisco:access_points:*:*:*:*:*:*:*:*
cpe:2.3:a:cisco:aironet_access_point_software:8.5\(151.0\):*:*:*:*:*:*:*
cpe:2.3:a:cisco:aironet_access_point_software:17.2.0.26:*:*:*:*:*:*:*

More vulnerabilities in Cisco Wireless Lan Controller

CVE-2014-0703 — Critical (CVSS 10.0): Cisco Wireless LAN Controller (WLC) devices 7.4 before 7.4.110.0 distribute Aironet IOS software with a race condition…
CVE-2020-3560 — High (CVSS 8.6): A vulnerability in Cisco Aironet Access Points (APs) could allow an unauthenticated, remote attacker to cause a denial…
CVE-2018-0417 — High (CVSS 7.8): A vulnerability in TACACS authentication with Cisco Wireless LAN Controller (WLC) Software could allow an…
CVE-2014-0707 — High (CVSS 7.8): Cisco Wireless LAN Controller (WLC) devices 7.2, 7.3, and 7.4 before 7.4.110.0 allow remote attackers to cause a denial…
CVE-2014-0706 — High (CVSS 7.8): Cisco Wireless LAN Controller (WLC) devices 7.2 before 7.2.115.2, 7.3, and 7.4 before 7.4.110.0 allow remote attackers…
CVE-2020-3552 — High (CVSS 7.4): A vulnerability in the Ethernet packet handling of Cisco Aironet Access Points (APs) Software could allow an…

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