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Adaptive Security ApplianceApplication · Cisco

CVE-2021-40117

HIGH · 7.5 CVSS v3.1 Published 2021-10-27
Fix available
A fix is available. Upgrade to 6.2.3.17 / 6.4.0.13 or later.
See remediation →
84/100
Remediation priority · High
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 SSL/TLS message handler for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability exists because incoming SSL/TLS packets are not properly processed. An attacker could exploit this vulnerability by sending a crafted SSL/TLS packet to an affected device. A successful exploit could allow the attacker to cause 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

This is a vulnerability in the SSL/TLS message handler for Cisco ASA and FTD software where incoming SSL/TLS packets are not properly processed. An unauthenticated remote attacker can exploit this by sending a crafted SSL/TLS packet to cause the affected device to reload, resulting in a denial of service condition.

MitigationApply the Cisco security updates/patches for this vulnerability to affected ASA and FTD devices. Until patched, consider implementing network-level access controls to limit exposure of SSL/TLS interfaces to untrusted networks.

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:< 9.8.4.40
Secure Firewall Threat DefenseApplication
Affected:< 6.2.3.17>= 6.3.0, < 6.4.0.13>= 6.5.0, < 6.6.5>= 6.7.0, < 6.7.0.3>= 7.0.0, < 7.0.1
Adaptive Security Appliance SoftwareOperating system
Affected:>= 9.9.0, < 9.12.4.26>= 9.13.0, < 9.14.3.9>= 9.15.0, < 9.15.1.17>= 9.16.0, < 9.16.2.3
Asa 5512 X FirmwareOperating system
Affected:= 009.009\(002.085\)= 009.014\(002.106\)
Asa 5505 FirmwareOperating system
Affected:= 009.009\(002.085\)= 009.014\(002.106\)
Asa 5515 X FirmwareOperating system
Affected:= 009.009\(002.085\)= 009.014\(002.106\)
Asa 5525 X FirmwareOperating system
Affected:= 009.009\(002.085\)= 009.014\(002.106\)
Asa 5545 X FirmwareOperating system
Affected:= 009.009\(002.085\)= 009.014\(002.106\)

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
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/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 the Cisco device type
    Run 'show version' or check the device model to confirm whether it is a Cisco Adaptive Security Appliance (ASA) or Firepower Threat Defense (FTD) device
    Affected if Device is Cisco ASA or FTD
  2. Determine the ASA software version
    Run 'show version' on the ASA device and locate the version string (e.g., 9.8, 9.12, 9.14, etc.)
    Affected if Version is < 9.8.4.40, or >= 9.9.0 and < 9.12.4.26, or >= 9.13.0 and < 9.14.3.9, or >= 9.15.0 and < 9.15.1.17, or >= 9.16.0 and < 9.16.2.3, or matches specific firmware builds 009.009(002.085) or 009.014(002.106)
  3. Determine the FTD software version
    Run 'show version' on the FTD device and locate the version string (e.g., 6.2, 6.3, 6.4, etc.)
    Affected if Version is < 6.2.3.17, or >= 6.3.0 and < 6.4.0.13, or >= 6.5.0 and < 6.6.5, or >= 6.7.0 and < 6.7.0.3, or >= 7.0.0 and < 7.0.1
  4. Verify SSL/TLS interface exposure
    Run 'show interface' and check for interfaces accepting SSL/TLS traffic (e.g., SSL VPN, AnyConnect, SSL inspection). Use 'show run ssl' to view SSL-related configuration.
    Affected if Device has SSL/TLS services enabled and reachable (SSL VPN, webvpn, ssl inspection)

The device is affected if it runs Cisco ASA or FTD software matching any of the version ranges listed AND has SSL/TLS interfaces exposed to network traffic.

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
Upgrade available Upgrade to 6.2.3.17 / 6.4.0.13 / 6.6.5 or later
Fixed in 6.2.3.176.4.0.136.6.5
Interim mitigation

Apply the Cisco security updates/patches for this vulnerability to affected ASA and FTD devices. Until patched, consider implementing network-level access controls to limit exposure of SSL/TLS interfaces to untrusted networks.

Recommended fix High confidence

ASA: 9.8.4.40, 9.12.4.26, 9.14.3.9, 9.15.1.17, or 9.16.2.3 (depending on branch); FTD: 6.2.3.17, 6.4.0.13, 6.6.5, or 6.7.0.3 (depending on branch)

  1. 1. Identify the exact Cisco ASA or FTD device model and current software version using 'show version' command
  2. 2. Consult Cisco Security Advisory for CVE-2021-40117 at tools.cisco.com to determine the appropriate fixed release for your specific version branch
  3. 3. Download the fixed software version from Cisco Software Download center (software.cisco.com)
  4. 4. Upload the new software image to the device using FTP, SCP, or through the device's management interface
  5. 5. Verify the upgrade using 'show version' to confirm the new fixed version is installed
  6. 6. For ASA devices in multiple context mode, test in a maintenance window as reload will be required
  7. 7. After upgrade, verify SSL/TLS functionality is operational and the device is not experiencing unexpected reloads
Caveat Device reload is required after upgrade; test in maintenance window for production environments

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

Fix this in Adaptive Security Appliance Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.

Scan for this in your stack

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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-2021-40117 in production — separate from our analysis above.

No notes yet

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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