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Cloudflare Containers Vulnerability Exposes Customer Data

Cloudflare Containers Vulnerability Exposes Customer Data

First seen 25 Sep 2026, 15:24 UTC • •

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ThreatCluster AI
ThreatCluster •September 26, 2026 at 05:24 UTC
  • •Cloudflare fixed a vulnerability allowing data access from deleted containers.
  • •Residual data included sensitive files like SQLite databases and credentials.
  • •Cloudflare implemented a two-stage fix to mitigate the issue.

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.

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Timeline

2026-04-22
CVE-2026-31431 published
Vulnerability assigned a CVE identifier and published in the National Vulnerability Database.
MITRE
2026-09-04
Vulnerability reported to Cloudflare
Oren Yomtov from Accomplish reported a flaw in Cloudflare Containers affecting data isolation.
Blog.Cloudflare
2026-09-14
Block wiping reactivated
Cloudflare reactivated block wiping for newly assigned storage to prevent further exploitation.
Techjuice.Pk
2026-09-19
Cleanup completed
Cloudflare retired all running container disks and cleared caches to eliminate residual data.
Thehackernews

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