CVE-2016-6356

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of service disruption.

Exploit odds

3.0% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2016-10-28 10:59 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 00:50 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 3.0% in the next 30 days (EPSS).
• Severity: 7.5 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2016-10-28 10:59 UTC

Last modified

2026-06-17 00:50 UTC

Exploit probability

3.0% · EPSS, next 30 days

Weakness

CWE-20 · Improper input validation

Record status

Modified

Affected

• Cisco Email Security Appliance 3.3.1-09
• Cisco Email Security Appliance 7.1.0
• Cisco Email Security Appliance 7.1.1
• Cisco Email Security Appliance 7.1.2
• Cisco Email Security Appliance 7.1.3
• Cisco Email Security Appliance 7.1.4
• Cisco Email Security Appliance 7.1.5
• Cisco Email Security Appliance 7.3.0

Attack profile CVSS 3.0 · 7.5

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2016-6356.md and follow it. Check whether this project is affected by CVE-2016-6356. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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