# CVE-2024-20406: Cisco IOS XR Software Intermediate System-to-Intermediate System Denial of Service Vulnerability > An adjacent attacker can crash the IS-IS process on Cisco IOS XR devices using segment routing, causing a denial of service. - **Severity:** High 7.4 (`CVSS:3.1/AV:A/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:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** No - **Published:** 11 Sep 2024 - **Updated:** 11 Sep 2024 - **Also known as:** GHSA-7474-cqc3-4g2p ## What is CVE-2024-20406? CVE-2024-20406 is a high-severity denial of service vulnerability in Cisco Ios Xr, published on 11 Sep 2024. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description A vulnerability in the segment routing feature for the Intermediate System-to-Intermediate System (IS-IS) protocol of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient input validation of ingress IS-IS packets. An attacker could exploit this vulnerability by sending specific IS-IS packets to an affected device after forming an adjacency. A successful exploit could allow the attacker to cause the IS-IS process on all affected devices that are participating in the Flexible Algorithm to crash and restart, resulting in a DoS condition. Note: The IS-IS protocol is a routing protocol. To exploit this vulnerability, an attacker must be Layer 2-adjacent to the affected device and must have formed an adjacency. This vulnerability affects segment routing for IS-IS over IPv4 and IPv6 control planes as well as devices that are configured as level 1, level 2, or multi-level routing IS-IS type. Weakness: CWE-20 (Improper Input Validation) ## Which versions are affected by CVE-2024-20406? It affects 1 product. Products: Cisco Ios Xr. ## How do I fix CVE-2024-20406? No fix has been published for CVE-2024-20406 yet. Limit exposure of the affected software until one is available. ## Is CVE-2024-20406 being exploited? There is no known exploitation of CVE-2024-20406 in the wild and no public exploit code. ## Other vulnerabilities in Cisco Ios Xr - [CVE-2020-3118](https://insights.sbomify.com/CVE-2020-3118/): Cisco IOS XR Software Discovery Protocol Format String (high 8.8, exploited in the wild) - [CVE-2020-3569](https://insights.sbomify.com/CVE-2020-3569/): Cisco IOS XR Software DVMRP Memory Exhaustion (high 8.6, exploited in the wild) - [CVE-2020-3566](https://insights.sbomify.com/CVE-2020-3566/): Cisco IOS XR Software DVMRP Memory Exhaustion (high 8.6, exploited in the wild) - [CVE-2010-3035](https://insights.sbomify.com/CVE-2010-3035/): Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service (high 7.5, exploited in the wild) - [CVE-2022-20821](https://insights.sbomify.com/CVE-2022-20821/): Cisco IOS XR Open Port (medium 6.5, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2024-20406 and fix it if it is affected. What it is: CVE-2024-20406 is a high-severity denial of service vulnerability in Cisco Ios Xr, published on 11 Sep 2024. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2024-20406 in the wild and no public exploit code. Affected product: Cisco Ios Xr. 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-2024-20406/ (Markdown: https://insights.sbomify.com/CVE-2024-20406/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2024-20406 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-20406 - OSV: https://osv.dev/vulnerability/CVE-2024-20406 --- From sbomify Insights: https://insights.sbomify.com/CVE-2024-20406/ Summaries are generated and may contain mistakes; the official description above is the record.