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Secure Firewall Threat DefenseApplication · Cisco

CVE-2021-40125

MEDIUM · 6.5 CVSS v3.1 Published 2021-10-27
Fix available
A fix is available. Upgrade to 6.4.0.13 / 6.6.5 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable 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 Internet Key Exchange Version 2 (IKEv2) implementation of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, remote attacker to trigger a denial of service (DoS) condition on an affected device. This vulnerability is due to improper control of a resource. An attacker with the ability to spoof a trusted IKEv2 site-to-site VPN peer and in possession of valid IKEv2 credentials for that peer could exploit this vulnerability by sending malformed, authenticated IKEv2 messages to an affected device. A successful exploit could allow the attacker to trigger a reload of the device.

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 · moderate confidence

A resource management vulnerability in Cisco ASA and FTD software's IKEv2 implementation allows an authenticated attacker who can spoof a trusted VPN peer and possesses valid IKEv2 credentials to send malformed IKEv2 messages, triggering a device reload and denial of service.

MitigationApply the Cisco security updates for ASA and FTD software. Ensure IKEv2 credentials are properly secured and monitor for anomalous IKEv2 traffic patterns that may indicate credential compromise or spoofing attempts.

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
Secure Firewall Threat DefenseApplication
Affected:< 6.4.0.13>= 6.6.0, < 6.6.5>= 6.7.0, < 6.7.0.3>= 7.0.0, < 7.0.1
Adaptive Security Appliance SoftwareOperating system
Affected:>= 9.8.0, < 9.8.4.40>= 9.9.0, < 9.12.4.30>= 9.14.0, < 9.14.3.9>= 9.15.0, < 9.15.1.17>= 9.16.0, < 9.16.2
Asa 5512 X FirmwareOperating system
Affected:= 009.016\(001.025\)
Asa 5505 FirmwareOperating system
Affected:= 009.016\(001.025\)
Asa 5515 X FirmwareOperating system
Affected:= 009.016\(001.025\)
Asa 5525 X FirmwareOperating system
Affected:= 009.016\(001.025\)
Asa 5545 X FirmwareOperating system
Affected:= 009.016\(001.025\)
Asa 5555 X FirmwareOperating system
Affected:= 009.016\(001.025\)

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/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 product type and version
    Run 'show version' on the device CLI to determine if running Cisco ASA Software or Firepower Threat Defense (FTD) and note the exact version number
    Affected if The device runs Cisco ASA Software or FTD and the version falls within the affected ranges listed in the CVE advisory
  2. Verify IKEv2 is enabled
    Run 'show crypto ikev2' or 'show run crypto ikev2' to check if IKEv2 protocol is configured on the device
    Affected if IKEv2 is actively configured or enabled on the device
  3. Check for IKEv2 VPN configurations
    Run 'show crypto ipsec sa' or 'show run tunnel-group' to identify any IKEv2 VPN tunnels that are defined
    Affected if Any IKEv2 VPN tunnels or remote access/site-to-site configurations using IKEv2 are present
  4. Compare installed version to affected ranges
    Compare your exact version from step 1 against the affected version ranges: FTD < 6.4.0.13, 6.6.0 to < 6.6.5, 7.0.0 to < 7.0.1; ASA 9.8.0 to < 9.8.4.40, 9.9.0 to < 9.12.4.30, 9.14.0 to < 9.14.3.9, 9.15.0 to < 9.15.1.17, 9.16.0 to < 9.16.2; or specific firmware 009.016(001.025) for ASA 5505/5512X/5515X/5525X/5545X/5555X
    Affected if The installed version matches one of the affected version ranges

Device is affected if it runs a vulnerable ASA or FTD version within the listed ranges AND has IKEv2 protocol enabled or configured for VPN connections.

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 6.4.0.13 / 6.6.5 / 6.7.0.3 or later
Fixed in 6.4.0.136.6.56.7.0.3
Interim mitigation

Apply the Cisco security updates for ASA and FTD software. Ensure IKEv2 credentials are properly secured and monitor for anomalous IKEv2 traffic patterns that may indicate credential compromise or spoofing attempts.

Recommended fix High confidence

Minimum fixed versions: FTD 6.4.0.13, 6.6.5, 6.7.0.3, 7.0.1 | ASA 9.8.4.40, 9.12.4.30, 9.14.3.9, 9.15.1.17 (choose based on current branch)

  1. 1. Identify the current version of Cisco ASA Software or Firepower Threat Defense (FTD) by running 'show version' on the device
  2. 2. Based on the current version branch, determine the minimum fixed release from the Cisco advisory: For FTD 6.4.x, upgrade to 6.4.0.13 or later; For FTD 6.6.x, upgrade to 6.6.5 or later; For FTD 6.7.x, upgrade to 6.7.0.3 or later; For FTD 7.0.x, upgrade to 7.0.1 or later; For ASA 9.8.x, upgrade to 9.8.4.40 or later; For ASA 9.9.x-9.12.x, upgrade to 9.12.4.30 or later; For ASA 9.14.x, upgrade to 9
  3. 3. Download the appropriate fixed software image from Cisco (requires valid CCO account)
  4. 4. Upload the new software image to the device using 'copy' command or through the device management interface
  5. 5. Install the upgrade using the 'install' command (for FTD) or reload the device after the software upgrade (for ASA)
  6. 6. Verify the new version is running with 'show version' and confirm the IKEv2 vulnerability is resolved
Caveat Major version upgrades (e.g., 9.8 to 9.14) may require compatibility checks with existing VPN configurations and could affect feature availability; always review Cisco release notes before upgrading

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

Fix this in Secure Firewall Threat Defense Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,120
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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-2021-40125 in production — separate from our analysis above.

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What this is

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What belongs here
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