Cmterm-7975-sip.9-4-2sr4 -

If you have no budget for replacement and your threat model is forgiving (air-gapped voice network, no remote users), then 9.4.2sr4 will likely continue working for years. But if you connect to SIP trunks, cloud PBX, or allow BYOD – plan an upgrade.

However, as of 2025, running this firmware is a unless carefully segmented. No new CVEs will be patched. No TLS 1.2 support. No modern SIP extensions (notify with flow-tag, gruu, etc.). It is a fossil, but a reliable one. cmterm-7975-sip.9-4-2sr4

About the author: This article was compiled from Cisco documentation, public release notes, and operational experience from legacy UC deployments spanning 2008–2025. If you have no budget for replacement and