CLAIM-2026-09-28-04

The affected storage pools used Linux device mapper thin provisioning with skip_block_zeroing enabled and 64 KiB block sizes; when a block was reassigned to a new container, a smaller write changed only the written portion and the remainder could retain data from the block's previous owner.

Why it matters

The isolation people test is execution isolation. This failure is one layer below it, in block allocation, where no application-level test can see it.

Sources

• cloudflare2026how