CVE-2020-3191Network attack vector

Device reload via IPv6 DNS length validation

Published May 6, 2020 · Updated Nov 15, 2024

Improper input validation in Cisco ASA Software allows remote attackers to reload affected devices with crafted IPv6 DNS queries. The IPv6 DNS packet-processing path fails to validate a field length before processing a query that traverses the device. Exposure requires IPv6 configuration and at least two nonlocal IPv6 routes over which DNS can traverse; exploitation reloads the firewall and interrupts service.

CVSS severity8.6
High
EPSS probability1.82%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Cisco ASA Software allows remote attackers to reload affected devices with crafted IPv6 DNS queries. The IPv6 DNS packet-processing path fails to validate a field length before processing a query that traverses the device. Exposure requires IPv6 configuration and at least two nonlocal IPv6 routes over which DNS can traverse; exploitation reloads the firewall and interrupts service.

The record

CVE
CVE-2020-3191
Published
May 6, 2020
Updated
Nov 15, 2024
Vendor
ClamAV
Product
Cisco Adaptive Security Appliance (ASA) Software
Classifications
CWE-20, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 6, 2020CVE publishedPublication date reported by the CVE source.
  2. Nov 15, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Adaptive Security Appliance (ASA) Softwareversion=n/a

Published CVSS scores

5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
8.6Cisco PSIRTCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
8.6NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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