TeamCity security patch activation fails: "File (pluginUpdates...) does not exist"

Symptoms

When activating an auto-downloaded TeamCity security patch from Administration | Updates (/admin/admin.html?item=update), clicking Activate opens an Install dialog. Clicking Install produces no visible change, and the Activate button remains enabled. A second click on Activate surfaces an error of the form:

File (<TeamCity-data-dir>\system\caches\pluginUpdates\fix_<patch-name>_<version>) does not exist.

For example, on a server with data directory D:\ProgramData\JetBrains\TeamCity:

File (D:\ProgramData\JetBrains\TeamCity\system\caches\pluginUpdates\fix_CVE_2026_44413_1.0.3) does not exist.

The patch is never installed.

Reproduced on TeamCity 2025.11.4 (build 208157) and TeamCity 2026.1 (build 222521).

Cause

The auto-download flow records the cache path without the .zip extension. The downloaded artifact (fix_<patch-name>.zip) is either not written to disk or stored under a different name, so the subsequent install step fails the existence check on the composed path.

Tracked in Security update: Error "File does not exist", if "Activate" button was clicked several times.

Resolution

Install the security patch manually as a regular TeamCity plugin:

1. Download the patch .zip directly from the JetBrains plugins repository. The current list of patches and download URLs is in the TeamCity Security Patches article. As an example, CVE-2026-44413 is at https://download.jetbrains.com/teamcity/plugins/internal/fix_CVE_2026_44413.zip.
2. In TeamCity, navigate to Administration | Plugins.
3. Use Upload plugin zip to upload the downloaded .zip.
4. On TeamCity 2018.2 and later, the plugin loads without a server restart. On earlier versions (2017.1 to 2018.1), restart the server.

To eliminate the dependency on this patch plugin for current vulnerabilities, upgrade to the latest TeamCity version.