Unbounded HTTP/1 status-line and chunk-extension buffering in Mint causes memory-exhaustion DoS

Summary

Allocation of Resources Without Limits or Throttling vulnerability in elixir-mint mint allows a remote HTTP server to exhaust memory on the client host and cause a denial of service. Two HTTP/1 response-parser states accumulate server data without any cap. In lib/mint/http1.ex, decode_status_line/4 stores the unconsumed data in conn.buffer when the status line is incomplete, and decode_body/5 does the same for an unterminated chunk-extension line. Both wait for a CRLF the server never has to send, and conn.buffer is prepended to every subsequent socket message. The :max_header_list_size budget is wired only into decode_headers/5 and decode_trailer_headers/4, so neither of these states is covered by it. A malicious server, or one reached through an attacker-controlled redirect or a fetched URL, streams bytes indefinitely until the BEAM node is killed by the operating system out-of-memory handler. The chunk-extension variant is reached 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 0.1.0 before 1.10.0.

Timeline

1. Sep 4, 2026, 2:31 PM UTCCVE published
2. Sep 4, 2026, 7:32 PM UTCCISA SSVC assessment

   Exploitation: poc · Automatable: no · Technical impact: partial

3. Sep 4, 2026, 7:32 PM UTCRecord last updated

Affected versions

• mint

  From 0.1.0 · fixed in 1.10.0

• elixir-mint/mint

  Version range not reported

References 4