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Cloudflare Workers remote Spectre leakage security flaw

Vulnerability
First reported
Last updated
Happening score
H score 32
1 unique sources, 1 articles

Summary

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Researchers disclosed a remote Spectre weakness in Cloudflare Workers that leaked a JWT from a co-located Worker in production, exposing a cross-tenant memory-read risk. The demonstrated leakage reached 12 bits per second, far above the earlier 2021 result, and Cloudflare said the issue was mitigated in production. The attack did not require a V8 sandbox escape or native code execution, but it showed that shared-process isolation could still permit sensitive data leakage.

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Timeline

  1. 19.08.2026 22:02 2 articles · 2h ago

    Researchers disclose remote Spectre leakage in Cloudflare Workers

    Initial Disclosure

    Researchers disclosed a remote Spectre attack against Cloudflare Workers that leaked a JSON Web Token (JWT) from a co-located Worker in production at up to 12 bits per second. Cloudflare said it had already mitigated the issue in production by improving Dynamic Process Isolation (DyPrIs), integrating the V8 Sandbox, and deploying Memory Protection Keys (MPK)-based in-process isolation, and the research paper said no customer data was accessed.

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