Report: CVE-2026-42786 - WebSocket fragmented message reassembly unbounded in bandit

Report: CVE-2026-42786 - WebSocket fragmented message reassembly unbounded in bandit

CVE ID :CVE-2026-42786 Published : May 1, 2026, 9:16 p.m. | 17 minutes ago Description :Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion. The fragment reassembly path in 'Elixir.Bandit.WebSocket.Connection':handle_frame/3 in lib/bandit/websocket/connection.ex appends every incoming Continuation{fin: false} frame's payload to a per-connection iolist with no cumulative size cap. The existing max_frame_size option only bounds individual frames; a peer that streams an unbounded number of continuation frames without ever setting fin=1 grows BEAM heap linearly until the OS or a supervisor kills the process. Because the accumulation happens before WebSock.handle_in/2 is called, the application has no opportunity to interpose a size check. Phoenix Channels and LiveView both run over WebSock on Bandit, so a stock Phoenix application exposes this surface as soon as it accepts socket connections. This issue affects bandit: from 0.5.0 before 1.11.0. Severity: 8.7 | HIGH Visit the link for more details, such as CVSS details, affected products, timeline, and more...

CVE Details

Severity
HIGH
Published
May 1, 2026
Impact: denial of service