Werk #19774: Handle corrupted data files gracefully instead of crashing

Component

Core & setup

Title

Handle corrupted data files gracefully instead of crashing

Date

Apr 14, 2026

Level

Trivial Change

Class

Bug Fix

Compatibility

Compatible - no manual interaction needed

Checkmk versions & editions

2.6.0b1 Not yet released	Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT
2.5.0b5 Not yet released	Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT

When a Checkmk data file (.mk file) became corrupted (e.g., filled with null bytes due to a filesystem issue), loading it would crash with a SyntaxError: source code string cannot contain null bytes. This was most commonly observed on the notification analysis page when the notification backlog file was corrupted.

Checkmk now gracefully falls back to the default value when a data file cannot be deserialized, and logs a warning.

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