CVE-2021-1402

FAUCET Score

CVE-2021-1402 is a high-severity denial-of-service (DoS) vulnerability affecting Cisco Firepower Threat Defense (FTD) Software. It stems from insufficient validation of software-based SSL/TLS messages, allowing an unauthenticated, remote attacker to trigger a device reload. The attack requires no user interaction and has a CVSS score of 8.6, indicating a high impact on availability. While there is no known public exploit code or active exploitation, the vulnerability has garnered some community discussion and media coverage.

Impacted Technologies

Vendor	Product	Version(s)	CPE
		>= 6.3.0, < 6.4.0CPE matchmatch criteria	cpe:2.3:a:cisco:firepower_threat_defense::::::::
		>= 6.5.0, < 6.6.0CPE 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

1.39%

Probability of exploitation in next 30 days

EPSS Percentile

69.4%

Percentile rank of EPSS score among Peer Group

As of 2026-07-26

Model: v2026.06.15

This CVE's current EPSS score of 0.0139 is in the 50th percentile among its peer group of 51,485 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

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-ssl-decrypt-dos-DdyLuK6c

Vendor Advisory