Mmastodon TechnologyCybersecurity first seen 10 h ago, last 10 h ago, peak #8

Cloudflare fixes cross-tenant data exposure in Containers sandboxes

Original: 🤖 Cloudflare Containers/Sandboxes cross-tenant data exposure: dm-thin storage pools ran with skip_block_zeroing, so a Wo

A cross-tenant data exposure flaw in Cloudflare's Containers and Sandboxes has been disclosed and fixed. The issue stemmed from dm-thin storage pools running with skip_block_zeroing enabled, meaning newly written 4 KiB pages into unmapped 64 KiB blocks could leave residual data on raw devices. A Workers Paid tenant could reportedly read up to 60 KiB of data left behind by a previous tenant from /dev/vdc. Cloudflare has patched the issue, and security communities are discussing the implications of shared-storage isolation failures in multi-tenant cloud platforms.

Why now: Security researchers are discussing a newly disclosed and fixed isolation flaw that could have exposed one cloud tenant's data to another.

CloudflareCloudflare ContainersCloudflare SandboxesCloudflare Workers

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Evidence

• 🤖 Cloudflare Containers/Sandboxes cross-tenant data exposure: dm-thin storage pools ran with skip_block_zeroing, so a Workers Paid tenant could write 4 KiB into each unmapped 64 KiB block, then raw-read /dev/vdc and recover up to 60 KiB left by a previous tenant. Fixed… · cloud@infosec.exchange · 2

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