safety security
The Timer Was Outside the Sandbox
Researchers amplified remote timing signals to leak a co-tenant JWT at up to 12 bits per second before Cloudflare deployed stronger isolation.
Summary
Researchers amplified remote timing signals to leak a co-tenant JWT at up to 12 bits per second before Cloudflare deployed stronger isolation.
The attack targeted the production security boundary used by Cloudflare Workers, where language-level isolation and restricted timers are intended to constrain co-located tenants. The researchers combined microarchitectural amplification with remote timing sources, reporting a Spectre-based extraction of a JWT token at up to 12 bits per second with 99.16 percent accuracy—orders of magnitude above the 2-bits-per-minute comparison they cite.
The paper also records a coordinated mitigation, not an unpatched disclosure. Cloudflare integrated the V8 Sandbox, improved its Dynamic Process Isolation detection, and deployed hardware-assisted memory-protection keys to separate tenant heaps. The result is evidence about one studied production architecture and attack path; it is not a claim that every edge runtime shares the flaw or that the disclosed route remains open.
Why it matters
Researchers amplified remote timing signals to leak a co-tenant JWT at up to 12 bits per second before Cloudflare deployed stronger isolation.
Limits and context
- The paper also records a coordinated mitigation, not an unpatched disclosure.
- The result is evidence about one studied production architecture and attack path; it is not a claim that every edge runtime shares the flaw or that the disclosed route remains open.
Key claims
Researchers amplified remote timing signals to leak a co-tenant JWT at up to 12 bits per second before Cloudflare deployed stronger isolation.
Qualification: The paper also records a coordinated mitigation, not an unpatched disclosure.
Evidence: source-2026-08-19-001
Sources
- arXiv preprint 2608.17043arXiv · primary research
Corrections
No corrections have been recorded for this story.