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CVE-2016-6406

35
FAUCET Score

CVE-2016-6406 is a critical vulnerability affecting Cisco Email Security Appliance (ESA) devices running specific AsyncOS versions (9.1.2, 9.7.2, 10.0.0) with the Enrollment Client before 1.0.2-065 installed. This flaw allows unauthenticated remote attackers to gain root access by connecting to an exposed testing/debugging interface. With a CVSS score of 9.8 (CRITICAL), the vulnerability is easily exploitable over the network with no user interaction, leading to complete compromise of confidentiality, integrity, and availability. While there is no evidence of active exploitation or public exploit code (Metasploit, Nuclei, ExploitDB), the vulnerability has garnered some community discussion and media coverage, indicating awareness within the security community.

Impacted Technologies

VendorProductVersion(s)CPE
9.1.2-023CPE matchmatch criteria
cpe:2.3:o:cisco:email_security_appliance_firmware:9.1.2-023:*:*:*:*:*:*:*
9.1.2-028CPE matchmatch criteria
cpe:2.3:o:cisco:email_security_appliance_firmware:9.1.2-028:*:*:*:*:*:*:*
9.1.2-036CPE matchmatch criteria
cpe:2.3:o:cisco:email_security_appliance_firmware:9.1.2-036:*:*:*:*:*:*:*
9.7.2-046CPE matchmatch criteria
cpe:2.3:o:cisco:email_security_appliance_firmware:9.7.2-046:*:*:*:*:*:*:*
9.7.2-047CPE matchmatch criteria
cpe:2.3:o:cisco:email_security_appliance_firmware:9.7.2-047:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.0

Exploit Intelligence

EPSS Score
3.57%
Probability of exploitation in next 30 days
EPSS Percentile
88.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0357 is in the 81st percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 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-20160922-esa
Vendor Advisory
securityfocus.com / bid/93116
Third Party AdvisoryVDB Entry
securitytracker.com / id/1036881