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Adaptive Security Appliance SoftwareOperating system · Cisco

CVE-2026-20020

MEDIUM · 5.7 CVSS v3.1 Published 2026-03-04
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
59/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A vulnerability in the OSPF protocol of Cisco Secure Firewall ASA Software and Cisco Secure FTD Software could allow an unauthenticated, adjacent attacker to cause an affected device to reload unexpectedly, resulting in a DoS condition. If OSPF authentication is enabled, the attacker must know the secret key to exploit this vulnerability. This vulnerability is due to insufficient input validation when processing OSPF update packets. An attacker could exploit this vulnerability by sending crafted OSPF update packets. A successful exploit could allow the attacker to create a buffer overflow, causing the affected device to reload, resulting in a DoS condition.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Buffer overflow vulnerability in Cisco ASA and FTD OSPF protocol implementation allows an adjacent unauthenticated attacker to send crafted OSPF update packets, causing a device reload and DoS condition. If OSPF authentication is enabled, the attacker requires knowledge of the secret key.

MitigationEnable OSPF authentication with a strong secret key and implement network segmentation to restrict adjacent attacker access to OSPF interfaces. Apply Cisco-provided software patches when available.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Adaptive Security Appliance SoftwareOperating system
Affected:= 9.12.1= 9.12.1.2= 9.12.1.3= 9.12.2= 9.12.2.1= 9.12.2.4= 9.12.2.5= 9.12.2.9= 9.12.3= 9.12.3.2= 9.12.3.7= 9.12.3.9
Secure Firewall Threat DefenseApplication
Affected:= 6.4.0= 6.4.0.1= 6.4.0.2= 6.4.0.3= 6.4.0.4= 6.4.0.5= 6.4.0.6= 6.4.0.7= 6.4.0.8= 6.4.0.9= 6.4.0.10= 6.4.0.11

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Adjacent
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify device product and version
    Run 'show version' on the device CLI and locate the software version string (e.g., 'Version 9.12.3' for ASA or 'Version 6.4.0.11' for FTD)
    Affected if The device runs Cisco ASA Software version 9.12.1, 9.12.1.2, 9.12.1.3, 9.12.2, 9.12.2.1, 9.12.2.4, 9.12.2.5, 9.12.2.9, 9.12.3, 9.12.3.2, 9.12.3.7, or 9.12.3.9, OR Cisco FTD version 6.4.0 through 6.4.0.11
  2. Verify OSPF is enabled
    Run 'show ospf' or 'show ospf interface' to confirm OSPF routing process is active and interfaces are participating in OSPF
    Affected if OSPF is running and the device participates in an OSPF area
  3. Check OSPF authentication configuration
    Run 'show ospf authentication' or examine OSPF interface configuration with 'show running-config interface' to see if message-digest (MD5) or HMAC authentication is configured
    Affected if OSPF authentication is not configured or uses a weak/shared secret key that could be compromised
  4. Confirm adjacency exposure
    Review network topology and OSPF neighbor adjacencies using 'show ospf neighbor' to determine if the device accepts OSPF packets from untrusted adjacent segments
    Affected if The device has OSPF neighbors on network segments accessible to untrusted or adjacent attackers

A device is affected if it runs an affected ASA or FTD version, has OSPF enabled, and either lacks OSPF authentication or uses authentication on segments accessible to adjacent attackers with knowledge of the secret key.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Enable OSPF authentication with a strong secret key and implement network segmentation to restrict adjacent attacker access to OSPF interfaces. Apply Cisco-provided software patches when available.

Recommended fix Moderate confidence

Contact Cisco TAC for specific fixed releases. ASA 9.12.x and FTD 6.4.x are affected; upgrade to latest available stable release per Cisco's remediation guidance.

  1. 1. Identify if OSPF is enabled on the affected Cisco ASA or FTD device
  2. 2. If OSPF is not required, disable it to eliminate the attack surface
  3. 3. If OSPF is required, ensure OSPF authentication is properly configured with a strong secret key
  4. 4. Contact Cisco TAC or check Cisco.com for the latest fixed software releases for this vulnerability
  5. 5. Plan maintenance window for upgrade implementation
  6. 6. Upgrade ASA Software to a version later than 9.12.2 (contact Cisco for specific fixed release)
  7. 7. Upgrade Firepower Threat Defense to a version later than 6.4.0.3 (contact Cisco for specific fixed release)
  8. 8. After upgrade, verify OSPF functionality is restored and the device is stable
Caveat Review Cisco release notes for potential behavioral changes in OSPF or other features between 9.12.x and the target release

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Adaptive Security Appliance Software Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
16.0 hours of engineering $2,760
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-20020 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
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  • Version or environment caveats, and links to real fixes
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