Bug ID 1959549: Upgrading to version 17.5.1 or later overwrites the #TMSH-VERSION in bigip_base.conf when the source UCS file is from a pre-17.5.0 version.

Last Modified: Jun 09, 2026

Affected Product(s):
BIG-IP Install/Upgrade(all modules)

Known Affected Versions:
17.5.1, 17.5.1.2, 17.5.1.3, 21.0.0, 21.0.0.1

Fixed In:
17.5.1.4

Opened: May 26, 2025

Severity: 2-Critical

Symptoms

When upgrading from versions prior to 17.5.0 to 17.5.1 or later, the #TMSH-VERSION marker in bigip_base.conf is overwritten with the target system version instead of preserving the source UCS version. This prevents the MCPD schema migration code from executing, potentially leading to configuration mismatches and missing schema-based workarounds.

Impact

Overwriting the #TMSH-VERSION in the bigip_base.conf file results in the wrong schema being used during configuration loading, leading to missed MCP schema-based workarounds.

Conditions

Roll-forward upgrades from versions 14.x, 15.x, 16.x, or 17.1.x to 17.5.1 and later releases are affected. Upgrades from version 17.5.x to 21.x and later versions are not impacted.

Workaround

None

Fix Information

None

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips