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Adaptive Security ApplianceApplication · Cisco

CVE-2020-3436

HIGH · 8.6 CVSS v3.1 Published 2020-10-21
Fix available
A fix is available. Upgrade to 6.3.0.6 / 6.4.0.10 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges 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 web services interface of Cisco Adaptive Security Appliance (ASA) and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to upload arbitrary-sized files to specific folders on an affected device, which could lead to an unexpected device reload. The vulnerability exists because the affected software does not efficiently handle the writing of large files to specific folders on the local file system. An attacker could exploit this vulnerability by uploading files to those specific folders. A successful exploit could allow the attacker to write a file that triggers a watchdog timeout, which would cause the device to unexpectedly reload, causing a denial of service (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

A vulnerability in the web services interface of Cisco ASA and FTD allows unauthenticated remote attackers to upload arbitrary-sized files to specific folders on the device. The software does not efficiently handle writing large files, which triggers a watchdog timeout causing an unexpected device reload and DoS condition.

MitigationApply the relevant Cisco software update/patch for ASA and FTD. Until patched, restrict or disable the web services interface from untrusted networks to reduce attack surface.

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 ApplianceApplication
Affected:< 9.6.4.45
Secure Firewall Threat DefenseApplication
Affected:<= 6.2.2>= 6.3.0, < 6.3.0.6>= 6.4.0, < 6.4.0.10>= 6.5.0, < 6.5.0.5= 6.6.0
Adaptive Security Appliance SoftwareOperating system
Affected:>= 9.8.0, < 9.8.4.25>= 9.9.0, < 9.9.2.80>= 9.10.0, < 9.10.1.44>= 9.12.0, < 9.12.4.2>= 9.13.0, < 9.13.1.12>= 9.14.0, < 9.14.1.15

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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 the device product type
    Run 'show version' on the device CLI. Look for 'Cisco Adaptive Security Appliance' or 'Firepower Threat Defense' in the output to confirm whether the device is an ASA or FTD appliance.
    Affected if The device runs ASA or FTD software
  2. Determine the installed ASA software version
    Run 'show version' and locate the 'Software Version' line. Note the full version number (for example, 9.8.4.10).
    Affected if The ASA version is < 9.6.4.45 OR falls within any of these ranges: >= 9.8.0 and < 9.8.4.25, >= 9.9.0 and < 9.9.2.80, >= 9.10.0 and < 9.10.1.44, >= 9.12.0 and < 9.12.4.2, >= 9.13.0 and < 9.13.1.12, >= 9.14.0 and < 9.14.1.15
  3. Determine the installed FTD software version
    For FTD, run 'show version' from the FTD CLI or use the command 'system' followed by 'show version' from admin context. Note the full version number (for example, 6.4.0.5).
    Affected if The FTD version is <= 6.2.2 OR falls within any of these ranges: >= 6.3.0 and < 6.3.0.6, >= 6.4.0 and < 6.4.0.10, >= 6.5.0 and < 6.5.0.5, or equals 6.6.0
  4. Verify if web services interface is enabled
    Run 'show running-config | include http' or 'show running-config | include web' to check if the ASDM/web management HTTP interface is configured. Also run 'show running-config vpn' to check for WebVPN configurations.
    Affected if HTTP server for ASDM or WebVPN is enabled and accessible from untrusted networks

The device is affected if it is a Cisco ASA or FTD running a version within the affected ranges AND has the web services interface (ASDM HTTP or WebVPN) enabled and exposed.

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.

From vendor data
Upgrade available Upgrade to 6.3.0.6 / 6.4.0.10 / 6.5.0.5 or later
Fixed in 6.3.0.66.4.0.106.5.0.5
Interim mitigation

Apply the relevant Cisco software update/patch for ASA and FTD. Until patched, restrict or disable the web services interface from untrusted networks to reduce attack surface.

Fix this in Adaptive Security Appliance Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,480
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,968.

Scan for this in your stack

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dbcve dependency scanner

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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-2020-3436 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
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data