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CVE-2020-3557

19
FAUCET Score

CVE-2020-3557 describes a denial-of-service vulnerability in Cisco Firepower Management Center (FMC) Software, specifically affecting the host input API daemon. This flaw, stemming from improper certificate validation, allows an unauthenticated, remote attacker to repeatedly restart the daemon by sending crafted data, leading to a continuous DoS condition for the API. Rated as Medium severity (CVSS 5.3), the attack is low complexity and requires no user interaction, though it only impacts availability. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 6.6.1CPE matchmatch criteria
cpe:2.3:a:cisco:secure_firewall_management_center:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
LOW
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.73%
Probability of exploitation in next 30 days
EPSS Percentile
50.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0073 is in the 31st percentile among its peer group of 23,725 CVEs.

Social Chatter

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

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 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-fmc-dos-3WymYWKh
Vendor Advisory