CVE-2026-71397 · Package
NO FIX YET · SEE WHAT TO DO
The grpc_server Elixir library does not enforce its max body size on client-streaming and bidirectional-streaming requests, so it buffers every chunk until a full message arrives. An unauthenticated attacker can send an oversized streamed message to exhaust memory and crash the node.
first public Nov 6, 2026 · 1 source
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Elixir services that run grpc_server 1.0.0 through 1.0.5 with the Cowboy adapter and expose client-streaming or bidirectional-streaming RPCs are exposed, since the streaming read path ignores max_body_size. Services that only use unary RPCs, or that are not reachable from untrusted clients, are less exposed. The sources do not say whether the flaw depends on any other configuration.
Not affected if not-internet-facing, unary-only-rpcs, version-1.0.6-or-later
Who cares cowboy, elixir, grpc, grpc_server
1.0.0 before 1.0.6.1.0.6 or laterAllocation of Resources Without Limits or Throttling vulnerability in elixir-grpc grpc_server allows unauthenticated attackers to exhaust memory and crash the node via an oversized client-streaming or bidirectional-streaming request body.
The streaming read clause of 'Elixir.GRPC.Server.Adapters.Cowboy.Handler':info/3 (grpc_server/lib/grpc/server/adapters/cowboy/handler.ex) never checks the configured max_body_size. Only the unary read path enforces that cap. 'Elixir.GRPC.Server.Adapters.Cowboy':reading_stream/1 (grpc_server/lib/grpc/server/adapters/cowboy.ex) appends every received chunk to its buffer until a complete length-prefixed message arrives. A client can declare a very large message and send it across many small HTTP/2 DATA frames, and the server buffers all of it.
This issue affects grpc_server: from 1.0.0 before 1.0.6.
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