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Identity Services EngineApplication · Cisco

CVE-2022-20756

HIGH · 7.5 CVSS v3.1 Published 2022-04-06
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges 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 RADIUS feature of Cisco Identity Services Engine (ISE) could allow an unauthenticated, remote attacker to cause the affected system to stop processing RADIUS packets. This vulnerability is due to improper handling of certain RADIUS requests. An attacker could exploit this vulnerability by attempting to authenticate to a network or a service where the access server is using Cisco ISE as the RADIUS server. A successful exploit could allow the attacker to cause Cisco ISE to stop processing RADIUS requests, causing authentication/authorization timeouts, which would then result in legitimate requests being denied access. Note: To recover the ability to process RADIUS packets, a manual restart of the affected Policy Service Node (PSN) is required. See the Details section for more information.

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 · high confidence

A denial-of-service vulnerability exists in Cisco ISE's RADIUS feature where improper handling of certain RADIUS requests allows an unauthenticated remote attacker to cause the Policy Service Node to stop processing RADIUS packets. Successful exploitation results in authentication/authorization timeouts for legitimate users, requiring manual PSN restart to restore functionality.

MitigationApply the Cisco vendor patch when available. Until then, consider network segmentation, rate limiting on RADIUS ports (1812/1813), and monitoring for unusual authentication patterns to detect potential exploitation 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
Identity Services EngineApplication
Affected:= 2.2.0= 2.4.0= 2.6.0= 2.7.0= 2.7.0.356= 3.0.0= 3.1

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

CVSS:3.1/AV:N/AC:L/PR:N/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 Cisco ISE installation and version
    Access the Cisco ISE admin interface or CLI and retrieve the installed software version. This is typically found in the Administration > System > Settings > Product Version or via the 'show version' command in the CLI.
    Affected if The installed version matches exactly: 2.2.0, 2.4.0, 2.6.0, 2.7.0, 2.7.0.356, 3.0.0, or 3.1
  2. Confirm RADIUS service is enabled
    Verify that the RADIUS feature is configured and active on the ISE deployment. Check in the ISE admin UI under Policy > Policy Elements > Results > RADIUS > RADIUS Server Sets, or check that the device is accepting RADIUS authentication requests on ports 1812/1813.
    Affected if RADIUS is actively configured and the ISE is acting as a RADIUS server for authentication/authorization requests
  3. Verify Policy Service Node is active
    In the ISE admin UI, navigate to Administration > System > Deployment and confirm that at least one Policy Service Node is registered and running. The vulnerability affects the PSN component specifically.
    Affected if A Policy Service Node is deployed and processing RADIUS requests
  4. Monitor for authentication failures
    Review RADIUS authentication logs and monitor for sudden spikes in failed or timed-out authentication attempts. Check the ISE operational logs and syslog exports for unusual patterns.
    Affected if Legitimate users experience authentication/authorization timeouts and the PSN stops processing RADIUS traffic

You are affected if Cisco ISE version is exactly 2.2.0, 2.4.0, 2.6.0, 2.7.0, 2.7.0.356, 3.0.0, or 3.1 AND the RADIUS feature with an active Policy Service Node is in use.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the Cisco vendor patch when available. Until then, consider network segmentation, rate limiting on RADIUS ports (1812/1813), and monitoring for unusual authentication patterns to detect potential exploitation attempts.

Recommended fix High confidence

Cisco ISE 2.7 Patch 4 (or latest 2.7.x patch)

  1. 1. Log in to Cisco ISE Administration GUI
  2. 2. Navigate to Administration > System > Upgrade > Upgrade Center
  3. 3. Download the Cisco ISE 2.7 Patch 4 (or latest available patch for 2.7) from Cisco
  4. 4. Backup the current ISE configuration
  5. 5. Install the patch on all Policy Service Nodes (PSN) in the deployment
  6. 6. After patch installation, verify RADIUS services are running: go to Operations > RADIUS > Live Logs
  7. 7. If services are not restored, restart the ISE services on each PSN via CLI: 'application stop ise' then 'application start ise'
  8. 8. Confirm RADIUS authentication is working properly
Caveat None expected - patch is intended to fix the vulnerability without changing functionality

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

Fix this in Identity Services Engine Scoped from the published advisory
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing8.0 h
  • Review / QA2.0 h
17.0 hours of engineering $2,900
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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-2022-20756 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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  • No spam, self-promotion, credentials, or personal data