Here are a few of the security vulnarabilities with Unified Communications manager 6. To find the full list, please follow the first link. Unfortunately I couldn't find any vulnarabilities for Cisco Unity but the security guide is last on the list...I hope this helps:

Cisco Security Advisories

http://www.cisco.com/en/US/products/products_security_advisories_listing.html

DoS and Authentication Bypass

http://www.cisco.com/en/US/products/products_security_advisory09186a00809b9011.shtml

DoS Vulnarabilities

http://www.cisco.com/en/US/products/products_security_advisory09186a0080995688.shtml

Disaster Recovery Command Execution

http://www.cisco.com/en/US/products/products_security_advisory09186a008096fd9a.shtml

SQL injection

http://www.cisco.com/en/US/products/products_security_advisory09186a0080949c7c.shtml

Phone Overflow and DoS vulnarabilities

http://www.cisco.com/en/US/products/products_security_advisory09186a0080949c7a.shtml

Some CCM5 vulnarabilities (may be related)

http://www.cisco.com/warp/public/707/cisco-sa-20060712-cucm.shtml

Cisco Unified Communications Manager Security Guide 6.0 (1)

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/security/6_0_1/secugd/secuview.html

Security Guide for Cisco Unity Release 5.x

http://www.cisco.com/en/US/docs/voice_ip_comm/unity/5x/security/guide/ex/5xcusecex.html

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