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CVE-2020-3480: Cisco IOS XE Software Zone-Based Firewall Denial of Service Vulnerabilities

• Severity: high (CVSS 8.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-09-24 · updated 2026-06-17
• Weakness: CWE-754

Description

Multiple vulnerabilities in the Zone-Based Firewall feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause the device to reload or stop forwarding traffic through the firewall. The vulnerabilities are due to incomplete handling of Layer 4 packets through the device. An attacker could exploit these vulnerabilities by sending a certain sequence of traffic patterns through the device. A successful exploit could allow the attacker to cause the device to reload or stop forwarding traffic through the firewall, resulting in a denial of service. For more information about these vulnerabilities, see the Details section of this advisory.

Affected products

• Cisco IOS XE: all versions

References

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-zbfw-94ckG4G
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-zbfw-94ckG4G

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