What is CVE-2016-6356?

CVE-2016-6356 is a high-severity vulnerability in Cisco Email Security Appliance, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2016-10-28.

How severe is CVE-2016-6356?

High severity. CVSS v3 base score is 7.5 out of 10.

Improper input validation in Cisco Email Security Appliance

CVE-2016-6356

A vulnerability in the email message filtering feature of Cisco AsyncOS Software for Cisco Email Security Appliances could allow an unauthenticated, remote attacker to cause an affected device to stop scanning and forwarding email messages due to a denial of service (DoS) condition. Affected Products: This vulnerability affects all releases prior to the first fixed release of Cisco AsyncOS Software for Cisco Email Security Appliances, both virtual and hardware appliances, if the software is configured to apply a message filter or content filter to incoming email attachments. The vulnerability is not limited to any specific rules or actions for a message filter or content filter. More Information: CSCuz63143. Known Affected Releases: 8.5.7-042 9.7.0-125. Known Fixed Releases: 10.0.0-125 9.1.1-038 9.7.2-047.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2016-10-28 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.030 (87.2th percentile), scored 2026-10-21.

Low probability of exploitation in the next 30 days, but still tracked. 87th percentile — 87.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.029 · newest: 0.030 · change: +0.001

Affected products

Cisco Email Security Appliance — versions 3.3.1-09, 7.1.0, 7.1.1
Cisco Asyncos Through 9.7.0-125 — versions Cisco AsyncOS through 9.7.0-125

Weakness classification (CWE)

CWE-20 — Improper Input Validation

References

www.securitytracker.com/id/1037122 (vdb-entry)
tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161026… (Vendor Advisory)
www.securityfocus.com/bid/93907 (vdb-entry)

Frequently asked questions

What is CVE-2016-6356?: CVE-2016-6356 is a high-severity vulnerability in Cisco Email Security Appliance, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2016-10-28.
How severe is CVE-2016-6356?: High severity. CVSS v3 base score is 7.5 out of 10.