# CVE-2021-1368: Memory corruption in Cisco NX-OS Software > An adjacent attacker can execute arbitrary code or cause denial of service on Cisco devices via crafted UDLD packets when the feature is enabled. - **Severity:** High 8.8 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 24 Feb 2021 - **Updated:** 8 Nov 2024 - **Also known as:** GHSA-jp9c-4gwx-v8x8 ## What is CVE-2021-1368? CVE-2021-1368 is a high-severity memory corruption vulnerability in Cisco Firepower Extensible Operating System, published on 24 Feb 2021. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description A vulnerability in the Unidirectional Link Detection (UDLD) feature of Cisco FXOS Software and Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to execute arbitrary code with administrative privileges or cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient input validation. An attacker could exploit this vulnerability by sending crafted Cisco UDLD protocol packets to a directly connected, affected device. A successful exploit could allow the attacker to execute arbitrary code with administrative privileges or cause the Cisco UDLD process to crash and restart multiple times, causing the affected device to reload and resulting in a DoS condition. Note: The UDLD feature is disabled by default, and the conditions to exploit this vulnerability are strict. The attacker needs full control of a directly connected device. That device must be connected over a port channel that has UDLD enabled. To trigger arbitrary code execution, both the UDLD-enabled port channel and specific system conditions must exist. In the absence of either the UDLD-enabled port channel or the system conditions, attempts to exploit this vulnerability will result in a DoS condition. It is possible, but highly unlikely, that an attacker could control the necessary conditions for exploitation. The CVSS score reflects this possibility. However, given the complexity of exploitation, Cisco has assigned a Medium Security Impact Rating (SIR) to this vulnerability. Weakness: CWE-787 (Out-of-bounds Write) ## Which versions are affected by CVE-2021-1368? It affects 3 products. Products: Cisco Firepower Extensible Operating System, Cisco Nx-Os, Cisco Unified Computing System. ## How do I fix CVE-2021-1368? No fix has been published for CVE-2021-1368 yet. Limit exposure of the affected software until one is available. ## Is CVE-2021-1368 being exploited? There is no known exploitation of CVE-2021-1368 in the wild and no public exploit code. ## Other vulnerabilities in Cisco Firepower Extensible Operating System - [CVE-2018-0310](https://insights.sbomify.com/CVE-2018-0310/): Information disclosure in Cisco FXOS and NX-OS unknown (critical 9.8) - [CVE-2015-6435](https://insights.sbomify.com/CVE-2015-6435/): Command injection in n/a (critical 9.8) - [CVE-2020-3456](https://insights.sbomify.com/CVE-2020-3456/): Cisco FXOS Software Firepower Chassis Manager Cross-Site Request Forgery Vulnerability (high 8.8) - [CVE-2020-3172](https://insights.sbomify.com/CVE-2020-3172/): Cisco FXOS and NX-OS Software Cisco Discovery Protocol Arbitrary Code Execution and Denial of Service Vulnerability (high 8.8) - [CVE-2018-0395](https://insights.sbomify.com/CVE-2018-0395/): Cisco FXOS and NX-OS Software Link Layer Discovery Protocol Denial of Service Vulnerability (high 8.8) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-1368 and fix it if it is affected. What it is: CVE-2021-1368 is a high-severity memory corruption vulnerability in Cisco Firepower Extensible Operating System, published on 24 Feb 2021. 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-2021-1368 in the wild and no public exploit code. Affected product: Cisco Firepower Extensible Operating System. 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-2021-1368/ (Markdown: https://insights.sbomify.com/CVE-2021-1368/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-1368 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-1368 - OSV: https://osv.dev/vulnerability/CVE-2021-1368 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-1368/ Summaries are generated and may contain mistakes; the official description above is the record.