HTTP/2 request bodies made of 1-byte DATA frames amplify memory use in Bandit

Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 request body reader of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via a request body sent as many 1-byte DATA frames. do_read_data/5 in lib/bandit/http2/stream.ex keeps every DATA frame payload as its own list element until the read returns. The :length option of read_body/2 counts body bytes, not frames, so a body of 1-byte frames costs a list cell and a binary term per byte. Interleaving the frames across up to 500 concurrent streams per connection keeps each stream consuming its frames as they arrive; in the reporter's test, 100 streams held 25 to 40 MiB of stream process memory for 5 MB sent. Only routes whose Plug reads the request body are affected, which includes any route behind Plug.Parsers. This issue affects bandit: from 0.3.1 before 1.14.1.

Source published

28 Oct 2026 13:26:25 UTC

Source modified

28 Oct 2026 13:26:25 UTC

Observed here

28 Oct 2026 14:46:48 UTC

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CVSS 4.0 · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N