Identity Services EngineApplication · Cisco
CVE-2023-20243
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 · uneditedA vulnerability in the RADIUS message processing 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 accounting requests. An attacker could exploit this vulnerability by sending a crafted authentication request to a network access device (NAD) that uses Cisco ISE for authentication, authorization, and accounting (AAA). This would eventually result in the NAD sending a RADIUS accounting request packet to Cisco ISE. An attacker could also exploit this vulnerability by sending a crafted RADIUS accounting request packet to Cisco ISE directly if the RADIUS shared secret is known. A successful exploit could allow the attacker to cause the RADIUS process to unexpectedly restart, resulting in authentication or authorization timeouts and denying legitimate users access to the network or service. Clients already authenticated to the network would not be affected. Note: To recover the ability to process RADIUS packets, a manual restart of the affected Policy Service Node (PSN) may be required. For more information, see the Details ["#details"] section of this advisory.
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 confidenceA vulnerability in Cisco ISE's RADIUS message processing allows unauthenticated attackers to cause DoS by sending crafted authentication requests to NADs, which triggers malformed RADIUS accounting requests to the ISE PSN. This causes the RADIUS process to unexpectedly restart, denying legitimate user authentication/authorization until manual PSN restart.
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
= 3.1= 3.2CVSS 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
- Changed
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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 checksWork through these to decide whether this CVE applies to you.
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Identify if Cisco ISE is deployedCheck for Cisco ISE installation by reviewing network infrastructure documentation, or access the ISE admin interface via HTTPS and verify the Cisco ISE login page appears. Alternatively, run 'show version' in CLI to confirm the device is running Cisco ISE.Affected if The environment uses Cisco ISE for network access control.
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Check installed Cisco ISE versionIn the ISE CLI, run 'show version' and locate the version number in the output. In the web UI, navigate to Administration > System > Deployment and check the version column for each node.Affected if The version is 3.1.x or 3.2.x (matching the = 3.1 and = 3.2 notation in the affected products).
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Verify RADIUS processing is enabledIn the ISE web UI, go to Administration > System > Deployment and select each node. Check the Policy Services pane to confirm the 'Enable Policy Services' checkbox is selected, which enables RADIUS authentication and accounting services.Affected if RADIUS processing is enabled via Policy Services on the ISE node.
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Confirm PSN node configurationIn the ISE web UI, navigate to Administration > System > Deployment and identify nodes configured as Policy Service Nodes (PSN). A PSN handles RADIUS authentication and accounting requests from NADs.Affected if The affected ISE node is configured as a PSN that processes RADIUS accounting requests.
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Review NAD connection configurationIn the ISE web UI, go to Work Centers > Network Access > Network Access Devices (NADs). Review the configured NADs to confirm they send RADIUS accounting requests to this PSN node.Affected if NADs are configured to send RADIUS accounting traffic to the affected PSN, providing an attack vector for crafted requests.
A user is affected if they run Cisco ISE version 3.1.x or 3.2.x with a PSN node that has RADIUS accounting enabled and accessible to NADs, allowing unauthenticated attackers to send crafted requests that crash the RADIUS process.
Generated from the published advisory. Verify against your own configuration.
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.
From vendor dataApply Cisco ISE patches when available; in interim, restrict NAD management access and monitor for unusual RADIUS accounting traffic patterns to detect exploitation attempts.
Fix this in Identity Services Engine
Scoped from the published advisory
- Consultation3.0 h
- Implementation6.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-20243 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2023-20243 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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