CVE-2025-20343Network attack vector

Unauthenticated restart via rejected-endpoint comparison logic

Published Nov 5, 2025 · Updated Nov 5, 2025

Incorrect comparison in Cisco Identity Services Engine 3.4.0 through 3.4 Patch 3 allows remote attackers to trigger an unexpected restart. The RADIUS suppression logic incorrectly compares endpoint state while processing an access request for a MAC address already marked as rejected after a specific crafted request sequence. No authentication is required, but the default-enabled rejection setting must remain configured; successful exploitation restarts ISE and interrupts service.

CVSS severity8.6
High
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect comparison in Cisco Identity Services Engine 3.4.0 through 3.4 Patch 3 allows remote attackers to trigger an unexpected restart. The RADIUS suppression logic incorrectly compares endpoint state while processing an access request for a MAC address already marked as rejected after a specific crafted request sequence. No authentication is required, but the default-enabled rejection setting must remain configured; successful exploitation restarts ISE and interrupts service.

The record

CVE
CVE-2025-20343
Published
Nov 5, 2025
Updated
Nov 5, 2025
Vendor
ClamAV
Product
Cisco Identity Services Engine
Classifications
CWE-697, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 5, 2025CVE publishedPublication date reported by the CVE source.
  2. Nov 5, 2025Record 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=3.4.0
  2. Affected versionversion=3.4 Patch 1
  3. Affected versionversion=3.4 Patch 2
  4. Affected versionversion=3.4 Patch 3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Identity Services Engineversion=3.4.0; version=3.4 Patch 1; version=3.4 Patch 2; version=3.4 Patch 3

Published CVSS scores

7.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.6Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-697Incorrect Comparison
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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