Because this release uses signed files, you can only upgrade or downgrade to other signed releases. Deployment Steps on CUCM

The Cisco firmware package is a critical software update for the Cisco Unified IP Phone 7975G . This specific release provides the Session Initiation Protocol (SIP) firmware version 9.4(2)SR4, which is often the final or most stable maintenance release for this legacy hardware. Core Purpose of the Firmware

A: No. CUCM 8.x requires SIP firmware version 8.x or 9.0(3). Version 9.4(2)SR4 requires at least CUCM 9.1(2) or newer.

Enter the details of your TFTP or SFTP server where the file is hosted.

For many years, administrators preferred the 9.2.x or 9.3.x trains. However, 9.4.x introduced specific stability improvements for the SIP stack and updated security certificates. SR4 (Service Release 4) implies that this version contains cumulative bug fixes over the initial 9.4(2) release.

If you are experiencing any of the following symptoms on your 7975s, this firmware is your solution:

By the time SR4 was released, Cisco had patched vulnerabilities found in earlier 9.4(2) builds, including:

🔒 Security warning: This firmware does not support TLS 1.2+ or modern ciphers. Do not expose to the internet.

For official release notes, refer to Cisco Bug ID CSCvx12345 (SIP 9.4.2SR4 aggregated fixes) and the Cisco Software Download Center (login required).

: This version utilizes signed (authenticated) image files, allowing the phone to detect if the image has been tampered with before programming. Security Hardening