# CVE-2023-20243: Denial of service in Cisco Identity Services Engine Software > Unauthenticated remote attackers can cause Cisco ISE to stop processing RADIUS packets, denying network access to legitimate users. - **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** No - **Published:** 6 Sep 2023 - **Updated:** 2 Aug 2024 - **Also known as:** GHSA-64jj-6hmj-39jw ## What is CVE-2023-20243? CVE-2023-20243 is a high-severity denial of service vulnerability in Cisco Identity Services Engine, published on 6 Sep 2023. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description A 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. Weakness: CWE-755 (Improper Handling of Exceptional Conditions), CWE-399 ## Which versions are affected by CVE-2023-20243? It affects 1 product. Products: Cisco Identity Services Engine. ## How do I fix CVE-2023-20243? No fix has been published for CVE-2023-20243 yet. Limit exposure of the affected software until one is available. ## Is CVE-2023-20243 being exploited? There is no known exploitation of CVE-2023-20243 in the wild and no public exploit code. ## Other vulnerabilities in Cisco Identity Services Engine - [CVE-2026-76460](https://insights.sbomify.com/CVE-2026-76460/): Cisco Identity Services Engine Incorrect Use of Privileged APIs (critical 10.0, exploited in the wild) - [CVE-2025-20337](https://insights.sbomify.com/CVE-2025-20337/): Cisco Identity Services Engine Injection (critical 10.0, exploited in the wild) - [CVE-2025-20281](https://insights.sbomify.com/CVE-2025-20281/): Cisco Identity Services Engine Injection (critical 10.0, exploited in the wild) - [CVE-2026-20130](https://insights.sbomify.com/CVE-2026-20130/): Cisco Identity Services Engine Hardening Release - Improper Neutralization Vulnerabilities (critical 10.0) - [CVE-2026-20192](https://insights.sbomify.com/CVE-2026-20192/): Cisco Identity Services Engine Hardening Release - Access Control Vulnerabilities (critical 10.0) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2023-20243 and fix it if it is affected. What it is: CVE-2023-20243 is a high-severity denial of service vulnerability in Cisco Identity Services Engine, published on 6 Sep 2023. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2023-20243 in the wild and no public exploit code. Affected product: Cisco Identity Services Engine. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2023-20243/ (Markdown: https://insights.sbomify.com/CVE-2023-20243/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2023-20243 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-20243 - OSV: https://osv.dev/vulnerability/CVE-2023-20243 --- From sbomify Insights: https://insights.sbomify.com/CVE-2023-20243/ Summaries are generated and may contain mistakes; the official description above is the record.