CVE-2020-3577

What it is

A vulnerability in the ingress packet processing path of Cisco Firepower Threat Defense (FTD) Software for interfaces that are configured either as Inline Pair or in Passive mode could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition. The vulnerability is due to insufficient validation when Ethernet frames are processed. An attacker could exploit this vulnerability by sending malicious Ethernet frames through an affected device. A successful exploit could allow the attacker do either of the following: Fill the /ngfw partition on the device: A full /ngfw partition could result in administrators being unable to log in to the device (including logging in through the console port) or the device being unable to boot up correctly. Note: Manual intervention is required to recover from this situation. Customers are advised to contact the Cisco Technical Assistance Center (TAC) to help recover a device in this condition. Cause a process crash: The process crash would cause the device to reload. No manual intervention is necessary to recover the device after the reload.

At a glance

Exploitability

Can be exploited from the same network segment without logging in. High risk of service disruption.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2020-10-21 19:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-08-11 19:37 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 7.4 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2020-10-21 19:15 UTC

Last modified

2026-08-11 19:37 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-20 · Improper input validation

Record status

Modified

Affected

• Cisco Secure Firewall Threat Defense < 6.3.0.6
• Cisco Secure Firewall Threat Defense < 6.4.0.10
• Cisco Secure Firewall Threat Defense < 6.5.0.5
• Cisco Secure Firewall Threat Defense < 6.6.1

Attack profile CVSS 3.1 · 7.4

Attack vector

Adjacent network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2020-3577.md and follow it. Check whether this project is affected by CVE-2020-3577. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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