{"id":"EEF-CVE-2026-42786","summary":"WebSocket fragmented message reassembly unbounded in bandit","details":"## Summary\n\nAllocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion.\n\nThe 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.\n\nBecause 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.\n\nThis issue affects bandit: from 0.5.0 before 1.11.0.\n\n## Configuration\n\nThe application must accept WebSocket connections. Applications that expose no WebSocket endpoints are not affected.","aliases":["CVE-2026-42786","GHSA-pf94-94m9-536p"],"modified":"2026-05-04T17:30:18.087113Z","published":"2026-05-01T20:34:17.014Z","database_specific":{"capec_ids":["CAPEC-130"],"cwe_ids":["CWE-770"],"cpe_ids":["cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"]},"references":[{"type":"ADVISORY","url":"https://github.com/mtrudel/bandit/security/advisories/GHSA-pf94-94m9-536p"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-42786.html"},{"type":"FIX","url":"https://github.com/mtrudel/bandit/commit/21612c7c7b1ce43eccd36d3af3a2299d23513667"},{"type":"PACKAGE","url":"https://hex.pm/packages/bandit"}],"affected":[{"package":{"name":"bandit","ecosystem":"Hex","purl":"pkg:hex/bandit"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.5.0"},{"fixed":"1.11.0"}]}],"versions":["0.5.0","0.5.1","0.5.2","0.5.3","0.5.4","0.5.5","0.5.6","0.5.7","0.5.8","0.5.9","0.5.10","0.5.11","0.6.0","0.6.1","0.6.2","0.6.3","0.6.4","0.6.5","0.6.6","0.6.7","0.6.8","0.6.9","0.6.10","0.6.11","0.7.0","0.7.1","0.7.2","0.7.3","0.7.4","0.7.5","0.7.6","0.7.7","1.0.0-pre.1","1.0.0-pre.2","1.0.0-pre.3","1.0.0-pre.4","1.0.0-pre.5","1.0.0-pre.6","1.0.0-pre.7","1.0.0-pre.8","1.0.0-pre.9","1.0.0-pre.10","1.0.0-pre.11","1.0.0-pre.12","1.0.0-pre.13","1.0.0-pre.14","1.0.0-pre.15","1.0.0-pre.16","1.0.0-pre.17","1.0.0-pre.18","1.0.0","1.1.0","1.1.1","1.1.2","1.1.3","1.2.0","1.2.1","1.2.2","1.2.3","1.3.0","1.4.0","1.4.1","1.4.2","1.5.0","1.5.1","1.5.2","1.5.3","1.5.4","1.5.5","1.5.6","1.5.7","1.6.0","1.6.1","1.6.2","1.6.3","1.6.4","1.6.5","1.6.6","1.6.7","1.6.8","1.6.9","1.6.10","1.6.11","1.7.0","1.8.0","1.9.0","1.10.0","1.10.1","1.10.2","1.10.3","1.10.4"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-42786.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/mtrudel/bandit","events":[{"introduced":"8909391f486d42138c5308410bc5ea49a65f4d46"},{"fixed":"21612c7c7b1ce43eccd36d3af3a2299d23513667"}]}],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-42786.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}],"credits":[{"name":"Peter Ullrich","type":"FINDER"},{"name":"Mat Trudel","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen","type":"ANALYST"}]}