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Cloudflare Containers vulnerability allowed data leakage | brief

Scworld • September 25, 2026

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 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

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This article is one source in a clustered incident — the cluster page carries the summary, timeline and every other outlet covering it.

Cloudflare Containers Vulnerability Exposes Customer Data On September 4, 2026, Oren Yomtov from Accomplish reported a vulnerability in Cloudflare Containers that allowed customers to access residual disk data from deleted containers of other accounts. The flaw stemmed from the use of Linux thin provisioning, which failed to wipe data before reassigning storage blocks. Researchers successfully retrieved sensitive data, including SQLite databases and credential files, from 18 out of 24 attempts across multiple servers. Cloudflare addressed the issue in two stages: reactivating block wiping on September 14 and retiring affected container disks by September 19. No evidence of malicious exploitation was found, and all recovered data was securely deleted. This incident highlights ongoing concerns about container security and the potential for data leaks in multi-tenant environments. 7 sources 57

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Cloudflare Containers vulnerability allowed data leakage | brief

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Extracted Entities

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