WebSocket fragmented message reassembly unbounded in bandit_CVE-2026-42786

{
    "lastseen": "",
    "description": "Allocation 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.",
    "published": "2026-05-01T20:34:17.014Z",
    "modified": "2026-05-01T20:34:17.014Z",
    "type": "cve",
    "title": "WebSocket fragmented message reassembly unbounded in bandit",
    "source": "EEF",
    "references": "https://github.com/mtrudel/bandit/security/advisories/GHSA-pf94-94m9-536p\nhttps://cna.erlef.org/cves/CVE-2026-42786.html\nhttps://osv.dev/vulnerability/EEF-CVE-2026-42786\nhttps://github.com/mtrudel/bandit/commit/21612c7c7b1ce43eccd36d3af3a2299d23513667",
    "id": "CVE-2026-42786",
    "bulletinFamily": "",
    "cwe": [
        "CWE-770"
    ],
    "cvelist": null,
    "sourceData": "mtrudel bandit 0.5.0\nmtrudel bandit 8909391f486d42138c5308410bc5ea49a65f4d46",
    "sourceHref": "",
    "cvss": {
        "score": 8.7,
        "severity": "HIGH",
        "vector": "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",
        "version": "4.0"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "bandit",
    "version": "0.5.0",
    "vendor": "mtrudel",
    "ai_description": "Allocation of Resources Without Limits or Throttling vulnerability allowing unauthenticated remote denial of service via memory exhaustion",
    "ai_severity": "High",
    "ai_vendor": "mtrudel",
    "ai_product": "bandit",
    "ai_version": "0.5.0 to 1.11.0",
    "ai_score": 8.7
}