---
id: "CVE-2020-3259"
kind: "vulnerability"
aliases: ["CVE-2020-3259"]
title: "A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco\u2026"
severity: "high"
cvss: 7.5
epss: null
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD)", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "cisco secure firewall threat defense", "fixed": ["6.2.3.16"], "affected": ">= 6.2.3, < 6.2.3.16", "ecosystem": "vendor"}, {"name": "cisco secure firewall threat defense", "fixed": ["6.3.0.6"], "affected": ">= 6.3.0, < 6.3.0.6", "ecosystem": "vendor"}, {"name": "cisco secure firewall threat defense", "fixed": ["6.4.0.9"], "affected": ">= 6.4.0, < 6.4.0.9", "ecosystem": "vendor"}, {"name": "cisco secure firewall threat defense", "fixed": ["6.5.0.5"], "affected": ">= 6.5.0, < 6.5.0.5", "ecosystem": "vendor"}, {"name": "cisco adaptive security appliance software", "fixed": ["9.8.4.20"], "affected": ">= 9.8, < 9.8.4.20", "ecosystem": "vendor"}, {"name": "cisco adaptive security appliance software", "fixed": ["9.9.2.67"], "affected": ">= 9.9, < 9.9.2.67", "ecosystem": "vendor"}, {"name": "cisco adaptive security appliance software", "fixed": ["9.10.1.40"], "affected": ">= 9.10, < 9.10.1.40", "ecosystem": "vendor"}, {"name": "cisco adaptive security appliance software", "fixed": ["9.12.3.9"], "affected": ">= 9.12, < 9.12.3.9", "ecosystem": "vendor"}, {"name": "cisco adaptive security appliance software", "fixed": ["9.13.1.10"], "affected": ">= 9.13, < 9.13.1.10", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["anyconnect", "cisco-asa", "cisco-ftd", "exploited", "infrastructure", "network-edge", "ransomware", "webvpn"]
not_affected_if: ["default-config", "no-anyconnect-or-webvpn"]
published_at: "2020-05-06T17:15:12+00:00"
first_seen_at: "2026-10-23T19:11:51+00:00"
updated_at: "2026-10-23T22:29:05+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2020-3259", "first_seen_at": "2026-10-23T19:11:51+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-3259", "first_seen_at": "2026-10-23T22:29:05+00:00"}]
---

# A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco…

Cisco ASA and FTD firewalls can leak chunks of device memory when they parse malformed URLs sent to the web services interface. An attacker can read confidential data from memory, and CISA lists it as actively exploited, including in ransomware campaigns.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) affected ? fixed ?
- vendor:cisco secure firewall threat defense affected >= 6.2.3, < 6.2.3.16 fixed 6.2.3.16
- vendor:cisco secure firewall threat defense affected >= 6.3.0, < 6.3.0.6 fixed 6.3.0.6
- vendor:cisco secure firewall threat defense affected >= 6.4.0, < 6.4.0.9 fixed 6.4.0.9
- vendor:cisco secure firewall threat defense affected >= 6.5.0, < 6.5.0.5 fixed 6.5.0.5
- vendor:cisco adaptive security appliance software affected >= 9.8, < 9.8.4.20 fixed 9.8.4.20
- vendor:cisco adaptive security appliance software affected >= 9.9, < 9.9.2.67 fixed 9.9.2.67
- vendor:cisco adaptive security appliance software affected >= 9.10, < 9.10.1.40 fixed 9.10.1.40
- vendor:cisco adaptive security appliance software affected >= 9.12, < 9.12.3.9 fixed 9.12.3.9
- vendor:cisco adaptive security appliance software affected >= 9.13, < 9.13.1.10 fixed 9.13.1.10

## How to check

Check whether AnyConnect or WebVPN is enabled on the ASA or FTD device; the flaw only affects those specific configurations.

## Fix

Apply the mitigation or fixed software release from Cisco's advisory for CVE-2020-3259, or discontinue use of the product if no mitigation is available (per CISA).

## Timeline

- 2026-10-23T19:11:51+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2020-3259
- 2026-10-23T22:29:05+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2020-3259

## From the sources

A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to retrieve memory contents on an affected device, which could lead to the disclosure of confidential information. The vulnerability is due to a buffer tracking issue when the software parses invalid URLs that are requested from the web services interface. An attacker could exploit this vulnerability by sending a crafted GET request to the web services interface. A successful exploit could allow the attacker to retrieve memory contents, which could lead to the disclosure of confidential information. Note: This vulnerability affects only specific AnyConnect and WebVPN configurations. For more information, see the Vulnerable Products section.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_