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No exploitation reportedFix available

CVE-2020-3563

No exploitation reported by the sources we read.

  • Published2020-10-21
  • Fixed in6.5.0.5 · 6.4.0.10 · 6.3.0.6
  • WeaknessCWE-400

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

A vulnerability in the packet processing functionality of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to inefficient memory management. An attacker could exploit this vulnerability by sending a large number of TCP packets to a specific port on an affected device. A successful exploit could allow the attacker to exhaust system memory, which could cause the device to reload unexpectedly. No manual intervention is needed to recover the device after it has reloaded.

Timeline

dates in UTC
  1. 2020-10-2119:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2020-3563?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-3563?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Cisco secure firewall threat defense
BranchAffectedFixed in
6.5≥ 6.5.0, < 6.5.0.56.5.0.5
6.4≥ 6.4.0, < 6.4.0.106.4.0.10
6.3≥ 6.3.0, < 6.3.0.66.3.0.6

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update Cisco secure firewall threat defense to 6.5.0.5 · 6.4.0.10 · 6.3.0.6

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • CISA-ADPSSVC decisionnone2024-11-13
  • OpenCVESSVC decisionnone—
  • NVDCVSS 3.18.6read 2026-10-23
  • CNACVSS 3.08.6read 2026-10-23
  • NVDCVSS 2.07.8read 2026-10-23
  • CNAweakness (CWE)CWE-400read 2026-10-23
  • NVDweakness (CWE)CWE-400read 2026-10-23
  • FIRST EPSSEPSS score1.4 %2026-10-22

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Published
2020-10-21
Last Modified
2026-08-11
NVD status
Modified

Frequently asked questions

What is CVE-2020-3563?

A vulnerability in the packet processing functionality of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to inefficient memory management. An attacker could exploit this vulnerability by sending a large number of TCP packets to a specific port on an affected device. A successful exploit could allow the attacker to exhaust system memory, which could cause the device to reload unexpectedly. No manual intervention is needed to recover the device after it has reloaded.

Is CVE-2020-3563 actively exploited?

Active exploitation of CVE-2020-3563 has not been confirmed. Its EPSS score was 1.4% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2020-3563?

CVE-2020-3563 has a CVSS v3 base score of 8.6 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H.

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