CVE-2020-3191

Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software IPv6 DNS Denial of Service Vulnerability

HIGH
8.6
CVSS Score
Published: May 6, 2020 at 04:41 PM UTC
Updated: August 11, 2026 at 07:33 PM UTC
26 products affected across 1 vendorAdaptive Security ApplianceSecure Firewall Threat DefenseASA 5512-x Firmware

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Severity
HIGH8.6
Exploit prediction
EPSS 2%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

9.10 ≤ v < 9.10.1.379.12 ≤ v < 9.12.2.99.6 ≤ v < 9.6.4.369.8 ≤ v < 9.8.4.129.9 ≤ v < 9.9.2.66
Affected range stops below 9.10.1.37, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.12.2.9, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.6.4.36, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.8.4.12, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.9.2.66, so it looks safe — our inference, not a vendor statement
cisco-asa-5505 (same device)
cisco-asa-5510 (same device)
cisco-asa-5512-x (same device)
cisco-asa-5515-x (same device)
cisco-asa-5520 (same device)
cisco-asa-5525-x (same device)
cisco-asa-5540 (same device)
cisco-asa-5545-x (same device)
cisco-asa-5550 (same device)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-20

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