CVE-2021-40125Network attack vector

Device reload via malformed authenticated IKEv2 messages

Published Oct 27, 2021 · Updated Nov 7, 2024

Denial of service in Cisco ASA Software allows remote authenticated users to reload affected devices with malformed IKEv2 messages. The IKEv2 implementation mishandles resource lifetime while processing an authenticated peer message, causing a use-after-free and device reload. Exploitation requires valid credentials for a spoofed trusted site-to-site VPN peer and a device configured with at least one IKEv2 site-to-site peer.

CVSS severity5.3
Medium
EPSS probability1.01%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Cisco ASA Software allows remote authenticated users to reload affected devices with malformed IKEv2 messages. The IKEv2 implementation mishandles resource lifetime while processing an authenticated peer message, causing a use-after-free and device reload. Exploitation requires valid credentials for a spoofed trusted site-to-site VPN peer and a device configured with at least one IKEv2 site-to-site peer.

The record

CVE
CVE-2021-40125
Published
Oct 27, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco Adaptive Security Appliance (ASA) Software
Classifications
CWE-400, CWE-416, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 27, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 7, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

ClamAV · Cisco Adaptive Security Appliance (ASA) Softwareversion=n/a

Published CVSS scores

6.3NIST National Vulnerability DatabaseAV:N/AC:M/Au:S/C:N/I:N/A:C
5.3Cisco Systems, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H/E:X/RL:X/RC:X
6.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
CWE-416Use After Free
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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