HTTP/1.1 must die: the desync endgame
Summary: PortSwigger researcher James Kettle published a paper arguing HTTP/1.1 has a fatal flaw in how request boundaries are delimited, enabling new classes of HTTP desync attacks that subverted core infrastructure at Akamai, Cloudflare, and Netlify. One Cloudflare case exposed over 24,000,000 websites to complete site takeover, and the toolkit and techniques yielded over $200,000 in bug bounties in a two-week period.
Bottom line: Six years of parser tightening and HTTP/2 have only hidden the problem, because CDNs that claim HTTP/2 support often downgrade requests to HTTP/1.1 for back-end transmission, and a single parser discrepancy in that chain can hand an attacker control of 24 million sites.
Read the original at PortSwigger Research ↗
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