CVE-2020-3191

What it is

A vulnerability in DNS over IPv6 packet processing for Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to unexpectedly reload, resulting in a denial of service (DoS) condition. The vulnerability is due to improper length validation of a field in an IPv6 DNS packet. An attacker could exploit this vulnerability by sending a crafted DNS query over IPv6, which traverses the affected device. An exploit could allow the attacker to cause the device to reload, resulting in a DoS condition. This vulnerability is specific to DNS over IPv6 traffic only.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of service disruption.

Exploit odds

1.9% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2020-05-06 17:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-08-11 19:33 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.9% in the next 30 days (EPSS).
• Severity: 8.6 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2020-05-06 17:15 UTC

Last modified

2026-08-11 19:33 UTC

Exploit probability

1.9% · EPSS, next 30 days

Weakness

CWE-20 · Improper input validation

Record status

Modified

Affected

• Cisco Secure Firewall Threat Defense < 6.2.3.16
• Cisco Secure Firewall Threat Defense < 6.3.0.6
• Cisco Secure Firewall Threat Defense < 6.4.0.6
• Cisco Asa 5505 Firmware 9.4\(1\)
• Cisco Asa 5505 Firmware 96.4\(0.42\)
• Cisco Asa 5510 Firmware 9.4\(1\)
• Cisco Asa 5510 Firmware 96.4\(0.42\)
• Cisco Asa 5512-x Firmware 9.4\(1\)

Attack profile CVSS 3.1 · 8.6

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

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Read https://cve-list.com/agent/cve/CVE-2020-3191.md and follow it. Check whether this project is affected by CVE-2020-3191. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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