Cloudflare Containers vulnerability allowed data leakage

As reported by The Hacker News, a security vulnerability discovered in Cloudflare Containers could have allowed a paying customer to access residual data left behind by other customers' containers on the same server. The issue stemmed from how shared disk space was managed, specifically concerning the reuse of data blocks.

The flaw resided in Cloudflare's use of thin provisioning for container disks, where deleted container blocks were returned to a shared pool without being wiped. This meant that data from previous containers could remain on these blocks. Researchers at Accomplish found that by writing a small amount of data to unused space and then reading the entire block at a raw disk level, they could access up to 60 kilobytes of leftover data from a prior container. This data included directory structures, database pages, and even SQLite databases.

Cloudflare confirmed the vulnerability affected its Containers and Sandboxes services, including those used for running AI agent code. The company has since fixed the issue by re-enabling block wiping for new allocations and has cleared affected server caches and disks. Cloudflare stated it found no evidence of the vulnerability being exploited by unauthorized parties prior to its discovery.

Source: The Hacker News