CVE-2016-6372: Cisco Email Security Appliance

High severity, CVSS 7.5. EPSS: 1.6% chance of exploitation in the next 30 days.

A vulnerability in the email message and content filtering for malformed Multipurpose Internet Mail Extensions (MIME) headers of Cisco AsyncOS Software for Cisco Email Security Appliances (ESA) and Web Security Appliances (WSA) could allow an unauthenticated, remote attacker to bypass the filtering functionality of the targeted device. Emails that should have been quarantined could instead be processed. Affected Products: This vulnerability affects all releases prior to the first fixed release of Cisco AsyncOS Software for Cisco ESA and Cisco WSA on both virtual and hardware appliances that are configured with message or content filters to scan incoming email attachments. More Information: CSCuy54740, CSCuy75174. Known Affected Releases: 9.7.1-066 9.5.0-575 WSA10.0.0-000. Known Fixed Releases: 10.0.0-125 9.1.1-038 9.7.2-047.

Affected products

• Cisco Email Security Appliance: version 8.0.1-023 only; version 8.0_base only; version 8.5.0-000 only; version 8.5.0-er1-198 only; version 8.5.6-052 only; version 8.5.6-073 only; …
• Cisco Web Security Appliance: version 5.6.0-623 only; version 6.0.0-000 only; version 7.1.0 only; version 7.1.1 only; version 7.1.2 only; version 7.1.3 only; …
• Cisco Web Security Appliance 8.0.5: version hot_patch_1 only

Published 2016-10-28. Last modified 2026-06-17.