CVE-2021-40125

What it is

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.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of service disruption.

Exploit odds

1.0% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-10-27 19:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-08-11 19:37 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.0% in the next 30 days (EPSS).
• Severity: 5.3 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-10-27 19:15 UTC

Last modified

2026-08-11 19:37 UTC

Exploit probability

1.0% · EPSS, next 30 days

Weakness

CWE-416 · Use after free

Record status

Modified

Affected

• Cisco Secure Firewall Threat Defense < 6.4.0.13
• Cisco Secure Firewall Threat Defense < 6.6.5
• Cisco Secure Firewall Threat Defense < 6.7.0.3
• Cisco Secure Firewall Threat Defense < 7.0.1
• Cisco Adaptive Security Appliance Software < 9.8.4.40
• Cisco Adaptive Security Appliance Software < 9.12.4.30
• Cisco Adaptive Security Appliance Software < 9.14.3.9
• Cisco Adaptive Security Appliance Software < 9.15.1.17

Attack profile CVSS 3.1 · 5.3

Attack vector

Network

Complexity

High

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-40125.md and follow it. Check whether this project is affected by CVE-2021-40125. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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