# CVE-2018-15399: Cisco Adaptive Security Appliance TCP Syslog Denial of Service Vulnerability > Remote attackers can cause denial of service on Cisco ASA/FTD devices by exhausting TCP syslog buffers via man-in-the-middle attacks. - **Severity:** Medium 6.8 (`CVSS:3.1/AV:N/AC:H/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:** 5 Oct 2018 - **Updated:** 26 Nov 2024 - **Also known as:** GHSA-29pp-9vf2-x8xr ## What is CVE-2018-15399? CVE-2018-15399 is a medium-severity denial of service vulnerability in Cisco Adaptive Security Appliance Software, published on 5 Oct 2018. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description A vulnerability in the TCP syslog module of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to exhaust the 1550-byte buffers on an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to a missing boundary check in an internal function. An attacker could exploit this vulnerability by establishing a man-in-the-middle position between an affected device and its configured TCP syslog server and then maliciously modifying the TCP header in segments that are sent from the syslog server to the affected device. A successful exploit could allow the attacker to exhaust buffer on the affected device and cause all TCP-based features to stop functioning, resulting in a DoS condition. The affected TCP-based features include AnyConnect SSL VPN, clientless SSL VPN, and management connections such as Secure Shell (SSH), Telnet, and HTTPS. Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-400 (Uncontrolled Resource Consumption) ## Which versions are affected by CVE-2018-15399? It affects 2 products. Products: Cisco Adaptive Security Appliance Software, Cisco Secure Firewall Threat Defense. ## How do I fix CVE-2018-15399? No fix has been published for CVE-2018-15399 yet. Limit exposure of the affected software until one is available. ## Is CVE-2018-15399 being exploited? There is no known exploitation of CVE-2018-15399 in the wild and no public exploit code. ## Other vulnerabilities in Cisco Adaptive Security Appliance Software - [CVE-2025-20333](https://insights.sbomify.com/CVE-2025-20333/): Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow (critical 9.9, exploited in the wild) - [CVE-2016-6366](https://insights.sbomify.com/CVE-2016-6366/): Cisco Adaptive Security Appliance (ASA) SNMP Buffer Overflow (high 8.8, exploited in the wild) - [CVE-2026-20349](https://insights.sbomify.com/CVE-2026-20349/): Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection (high 8.6, exploited in the wild) - [CVE-2024-20353](https://insights.sbomify.com/CVE-2024-20353/): Cisco ASA and FTD Denial of Service (high 8.6, exploited in the wild) - [CVE-2016-6367](https://insights.sbomify.com/CVE-2016-6367/): Cisco Adaptive Security Appliance (ASA) CLI Remote Code Execution (high 7.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2018-15399 and fix it if it is affected. What it is: CVE-2018-15399 is a medium-severity denial of service vulnerability in Cisco Adaptive Security Appliance Software, published on 5 Oct 2018. 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-2018-15399 in the wild and no public exploit code. Affected product: Cisco Adaptive Security Appliance Software. 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-2018-15399/ (Markdown: https://insights.sbomify.com/CVE-2018-15399/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2018-15399 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-15399 - OSV: https://osv.dev/vulnerability/CVE-2018-15399 --- From sbomify Insights: https://insights.sbomify.com/CVE-2018-15399/ Summaries are generated and may contain mistakes; the official description above is the record.