Unbounded HTTP/1 response-header and chunked-trailer accumulation in Mint causes memory-exhaustion DoS

Summary

Allocation of resources without limits vulnerability in elixir-mint mint allows a remote HTTP server to exhaust memory on the client host and cause a denial of service. The Mint.HTTP1.decode_headers/5 and Mint.HTTP1.decode_trailer_headers/4 functions in lib/mint/http1.ex accumulate every parsed response header and chunked-trailer field into a per-request list that persists across incoming TCP segments as request.headers_buffer, and only clear it when the terminating blank line is received. The section has no cap on the number of headers or on total bytes, and the underlying :erlang.decode_packet(:httph_bin, binary, []) parser is invoked with an empty option list so its per-line and per-packet size limits also default to unlimited. A malicious HTTP server (reachable directly, via an attacker-controlled redirect, via SSRF, or via a man-in-the-middle) can stream complete header lines (or, after a chunked body, complete trailer lines) indefinitely without ever emitting the terminating blank line. The connection state grows without bound until the BEAM node is killed by the operating system's out-of-memory handler, taking down the entire application that uses Mint as an HTTP client. This issue affects mint: from 0.1.0 before 1.9.2.

Timeline

1. Jul 14, 2026, 8:36 AM UTCCVE published
2. Jul 14, 2026, 12:27 PM UTCCISA SSVC assessment

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

3. Jul 14, 2026, 3:07 PM UTCRecord last updated

Affected versions

• mint

  From 0.1.0 · fixed in 1.9.2

• elixir-mint/mint

  Version range not reported

References 4