EEF-CVE-2026-82729

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EEF-CVE-2026-82729

Summary: Quadratic chunk-size parsing in Mint.HTTP1.Parse allows CPU-exhaustion DoS

Details: ## Summary Inefficient Algorithmic Complexity vulnerability in elixir-mint mint allows a remote HTTP server to exhaust CPU on the client host and cause a denial of service. parse\_hex\_prefix/2 in lib/mint/http1/parse.ex folds each hex digit of a chunked response's chunk-size field into an arbitrary-precision accumulator with acc \* 16 + digit and imposes no limit on the digit count. Because the accumulator grows without bound, the multiplication is not constant time and one pass over N digits costs O(N squared). handle\_data/2 prepends conn.buffer and re-parses from the start on every socket message, so a server that dribbles the digits out in small packets makes the client pay that cost repeatedly. A run of roughly 512,000 hex digits costs over ten seconds of CPU in a single pass, measured on stock defaults. The parser reaches this state after a valid status line and a complete, valid header section, so an intermediary inspecting only headers sees an ordinary 200 response. This issue affects mint: from 1.9.3 before 1.10.0.

References: https://github.com/elixir-mint/mint/security/advisories/GHSA-7p8w-j234-7qc8, https://cna.erlef.org/cves/CVE-2026-82729.html, https://github.com/elixir-mint/mint/commit/bd2a4e7513594997c140cfef9fe0e968712fb588, https://hex.pm/packages/mint