CVE-2020-3179: Cisco Firepower Threat Defense Software Generic Routing Encapsulation Tunnel IPv6 Denial of Service Vulnerability

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-05-06 · updated 2026-08-11
Weakness: CWE-415

Description

A vulnerability in the generic routing encapsulation (GRE) tunnel decapsulation feature of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to a memory handling error when GRE over IPv6 traffic is processed. An attacker could exploit this vulnerability by sending crafted GRE over IPv6 packets with either IPv4 or IPv6 payload through an affected device. A successful exploit could allow the attacker to cause the device to crash, resulting in a DoS condition.

Affected products

Cisco Asa 5505 Firmware: 9.9(2), 101.5(1.26)
Cisco Asa 5510 Firmware: 9.9(2), 101.5(1.26)
Cisco Asa 5512-X Firmware: 9.9(2), 101.5(1.26)
Cisco Asa 5515-X Firmware: 9.9(2), 101.5(1.26)
Cisco Asa 5520 Firmware: 9.9(2), 101.5(1.26)
Cisco Asa 5525-X Firmware: 9.9(2), 101.5(1.26)
Cisco Asa 5540 Firmware: 9.9(2), 101.5(1.26)
Cisco Asa 5545-X Firmware: 9.9(2), 101.5(1.26)
Cisco Asa 5550 Firmware: 9.9(2), 101.5(1.26)
Cisco Asa 5555-X Firmware: 9.9(2), 101.5(1.26)
Cisco Asa 5580 Firmware: 9.9(2), 101.5(1.26)
Cisco Asa 5585-X Firmware: 9.9(2), 101.5(1.26)
Cisco Firepower Threat Defense Software: from 6.3.0 before 6.3.0.5; from 6.4.0 before 6.4.0.6 — fixed in 6.3.0.5, 6.4.0.6

How to fix

Upgrade to a fixed version: Cisco Firepower Threat Defense Software 6.3.0.5, 6.4.0.6. Check the vendor advisory for mitigations.

References

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