Consideration
In FME 2026.2 and specified versions containing the backported security updates, Version 0 of the TempPathnameCreator transformer may fail and produce this error:
@Tcl2 -- failed to evaluate expression `set sampleTempFile [FME_TempFilename]; set ourTempDir {}; append ourTempDir $sampleTempFile {_d}; file mkdir $ourTempDir; set env(TempPathnameCreator_c09e5e07_d9fb_441b_a564_c06824bd4ea42_dir) $ourTempDir; set env(TempPathnameCreator_c09e5e07_d9fb_441b_a564_c06824bd4ea42_file) $sampleTempFile; set gNumTempFilesHandedOut 0;' -- not allowed to invoke subcommand mkdir of file
This may occur when the security tier is set to the Default Hardening tier, which is configurable in the FME Workbench user interface in FME Form, FME Form CLI, or FME Flow System Configurations.
Security tiers can only be set by Administrators.
Why This Happens
As a result of security changes, the ability to specify some TCL and FME Functions in parameter and attribute values has been disabled or reduced, impacting some transformers and advanced scripting features. FME Hub items using this transformer may also be impacted.
This applies to the updated versions and instances that have been patched according to the instructions in the advisory:
FME Form versions:
- 2026.2
- 2026.1.0.1, 2026.1.1.1, 2026.1.2.1
- 2025.2.0.1, 2025.2.1.1, 2025.2.2.1, 2025.2.3.1, 2025.2.4.2
- 2025.1.0.2, 2025.1.1.1, 2025.1.2.1, 2025.1.3.5
- 2025.0.0.1, 2025.0.1.1, 2025.0.2.1, 2025.0.3.2
- 2024.2.0.1, 2024.2.1.1, 2024.2.2.1, 2024.2.3.1, 2024.2.4.1, 2024.2.5.2
FME Flow versions:
- 2026.2
- 2026.1.2.1
- 2025.2.4.2
- 2025.1.3.5
- 2025.0.3.2
- 2024.2.5.2
- FME Flow instances with the hotfix patch and upgraded engine installed per the resolution option for backported security fixes described in the FME November 2026 Security Updates:
- 2026.1.0.0 through 2026.1.2.0
- 2025.2.0.0 through 2025.2.4.1
- 2025.1.0.0 through 2025.1.3.4
- 2025.0.0.0 through 2025.0.3.1
- 2024.2.0.0 through 2024.2.5.1
How to Resolve It
We recommend upgrading to Version 1 of the TempPathnameCreator in all old workspaces. Refer to Working with Transformer Versions.
If your workflow includes the TempPathnameCreator as an embedded or linked custom transformer, please follow the steps outlined in How to Update a Custom Transformer to perform the upgrade.
Alternatively, changing the security tier to the Minimal Hardening tier will allow Version 0 of the TempPathnameCreator to work again.
Minimal Hardening is not recommended for most users.