Security readout for executives and security teams
Plain-English summary
CVE-2020-3191 is a denial-of-service flaw in Cisco ASA and FTD handling of DNS over IPv6. A remote unauthenticated attacker could trigger an unexpected device reload, interrupting firewall or security gateway availability.
Executive priority
Treat this as high priority where Cisco ASA or FTD protects critical networks and IPv6 DNS traffic is allowed. Business risk is outage, not data theft, but a firewall reload can disrupt protected services.
Technical view
The flaw is improper length validation in IPv6 DNS packet processing. Crafted DNS-over-IPv6 traffic that traverses an affected Cisco ASA or FTD device can cause a reload. The CVSS v3.0 score is 8.6 with network attack vector and high availability impact.
Likely exposure
Exposure depends on Cisco ASA or FTD deployment and whether DNS-over-IPv6 traffic can traverse the device. The provided sources do not list affected software versions in the bundle, so inventory must be checked against Cisco guidance.
Exploitation context
The source bundle does not indicate CISA KEV listing or active exploitation. Exploitation is described as remote and unauthenticated, but limited to DNS over IPv6 traffic traversing the affected device.
Researcher notes
Key unknowns in the provided bundle are affected version ranges, fixed releases, and operational mitigations. Validation should focus on IPv6 DNS traversal, Cisco software version mapping, and reload telemetry rather than proof-of-concept reproduction.
Mitigation direction
- Check Cisco's advisory for affected and fixed software releases.
- Upgrade Cisco ASA or FTD according to vendor guidance.
- Review whether DNS-over-IPv6 traversal is required through affected devices.
- Apply compensating controls only if vendor guidance supports them.
Validation and detection
- Inventory Cisco ASA and FTD devices in production paths.
- Confirm whether IPv6 DNS traffic can traverse each device.
- Compare running software releases with Cisco's advisory.
- Review device logs for unexpected reloads or DoS symptoms.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CWE-20: Exact CWE lookup
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Open ATT&CK lookupCVE-2020-3191 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.6 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H3.94Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
8.6HighVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20200506 Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software IPv6 DNS Denial of Service VulnerabilityCVE reference · vendor-advisory, x_refsource_CISCO
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.