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CVE-2020-3563

27
FAUCET Score

CVE-2020-3563 is a denial-of-service vulnerability in Cisco Firepower Threat Defense (FTD) Software, stemming from inefficient memory management. An unauthenticated, remote attacker can exploit this by sending numerous TCP packets to a specific port, leading to memory exhaustion and an unexpected device reload. With a CVSS score of 8.6 (High), this vulnerability requires no user interaction and has a high impact on availability. Despite its severity, there is no known active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
>= 6.3.0, < 6.3.0.6CPE matchmatch criteria
cpe:2.3:a:cisco:firepower_threat_defense:*:*:*:*:*:*:*:*
>= 6.4.0, < 6.4.0.10CPE matchmatch criteria
cpe:2.3:a:cisco:firepower_threat_defense:*:*:*:*:*:*:*:*
>= 6.5.0, < 6.5.0.5CPE matchmatch criteria
cpe:2.3:a:cisco:firepower_threat_defense:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

8.6HIGH

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
4.0
CvssVersion
3.0

Exploit Intelligence

EPSS Score
1.42%
Probability of exploitation in next 30 days
EPSS Percentile
70.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0141 is in the 51st percentile among its peer group of 51,551 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (1)

ciscovendor investigatingvia nvd_reference
View patch

References

tools.cisco.com / security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-tcp-dos-GDcZDqAf
Vendor Advisory