Bug 2568233 (CVE-2026-115701)

Summary: CVE-2026-115701 cowboy: cowboy: Denial of Service via memory exhaustion on keep-alive connections
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Cowboy. An unauthenticated remote attacker can cause a Denial of Service (DoS) by sending an excessive volume of data over an active HTTP persistent connection. Because Cowboy buffers incoming data without applying size limits while a request is being processed, continuous data transfer can exhaust system memory and crash the server.
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Description OSIDB Bzimport 2026-11-06 14:37:05 UTC 
Allocation of Resources Without Limits or Throttling vulnerability in ninenines cowboy allows an unauthenticated remote attacker to exhaust connection process memory over HTTP/1.1.

Once a request has been received in full and its handler is still running, cowboy_http:parse/2 in src/cowboy_http.erl appends every further byte that arrives on the keep-alive connection to the connection buffer and returns to the receive loop without parsing it. The socket stays in active mode and no limit applies to this buffer: max_request_line_length, max_headers and the other parser limits only take effect once the handler returns and parsing resumes, and the only timer in this state is idle_timeout (default 60 seconds), which is reset on every received chunk. A client can therefore send an arbitrary amount of data on one connection for as long as the handler runs, and a few connections to an endpoint that holds requests open can drive the Erlang VM into out-of-memory conditions.

This issue affects cowboy: from 2.18.0 onward.