CVE-2021-40125

Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software IKEv2 Site-to-Site VPN Denial of Service Vulnerability

MEDIUM
6.5
CVSS Score
Published: October 27, 2021 at 06:50 PM UTC
Updated: August 11, 2026 at 07:37 PM UTC
18 products affected across 1 vendorAdaptive Security ApplianceSecure Firewall Threat DefenseASA 5512-x Firmware

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Severity
MEDIUM6.5
Exploit prediction
EPSS 1%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

9.14.0 ≤ v < 9.14.3.99.15.0 ≤ v < 9.15.1.179.16.0 ≤ v < 9.16.29.8.0 ≤ v < 9.8.4.409.9.0 ≤ v < 9.12.4.30
Affected range stops below 9.12.4.30, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.14.3.9, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.15.1.17, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.16.2, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.8.4.40, so it looks safe — our inference, not a vendor statement
cisco-asa-5505 (same device)
cisco-asa-5512-x (same device)
cisco-asa-5515-x (same device)
cisco-asa-5525-x (same device)
cisco-asa-5545-x (same device)
cisco-asa-5555-x (same device)
cisco-asa-5580 (same device)
cisco-asa-5585-x (same device)
v < 6.4.0.136.6.0 ≤ v < 6.6.56.7.0 ≤ v < 6.7.0.37.0.0 ≤ v < 7.0.1

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-416CWE-400

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