{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0.5.9"
              },
              {
                "fixed": "1.11.0"
              }
            ],
            "source": "AFFECTED_FIELD"
          },
          "events": [
            {
              "introduced": "81f0928ec9e92bc70354015435896f03393b1c05"
            },
            {
              "fixed": "e62619895d0d2584d7ffa57d43ef6f72437dfaff"
            }
          ],
          "repo": "https://github.com/mtrudel/bandit",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-frh3-6pv6-rc8j"
  ],
  "database_specific": {
    "cna_assigner": "EEF",
    "cwe_ids": [
      "CWE-770"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39804.json",
    "unresolved_ranges": [
      {
        "extracted_events": [
          {
            "introduced": "da4027cff7d2b80319e76fe7a32f84beceec490a"
          },
          {
            "fixed": "8156921a51e684a951221da7bc30a70a022f722e"
          }
        ],
        "source": "AFFECTED_FIELD"
      }
    ]
  },
  "details": "Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion when WebSocket permessage-deflate compression is enabled.\n\n'Elixir.Bandit.WebSocket.PerMessageDeflate':inflate/2 in lib/bandit/websocket/permessage_deflate.ex calls :zlib.inflate/2 with no output-size cap, then materializes the entire decompressed payload as a single binary via IO.iodata_to_binary/1. The websocket_options.max_frame_size option only bounds the on-the-wire (compressed) frame size, not the decompressed output. A high-ratio compressed frame (e.g. uniform data at ~1024:1 ratio) can stay well under any wire-size limit while forcing GiB-scale heap allocations in the connection process before any application code runs.\n\nAn unauthenticated attacker who can open a WebSocket connection can send a single such frame to exhaust the BEAM node's memory and trigger an OOM kill.\n\nThis vulnerability requires both Bandit's server-level websocket_options.compress and the per-upgrade compress: true option passed to WebSockAdapter.upgrade/4 to be enabled. Stock Phoenix and LiveView applications are not affected as they default to compress: false.\n\nThis issue affects bandit: from 0.5.9 before 1.11.0.",
  "id": "CVE-2026-39804",
  "modified": "2026-08-04T11:31:01.605638570Z",
  "published": "2026-05-01T20:34:24.604Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://cna.erlef.org/cves/CVE-2026-39804.html"
    },
    {
      "type": "WEB",
      "url": "https://github.com"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-39804"
    },
    {
      "type": "WEB",
      "url": "https://repo.hex.pm"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39804.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/mtrudel/bandit/security/advisories/GHSA-frh3-6pv6-rc8j"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-39804"
    },
    {
      "type": "FIX",
      "url": "https://github.com/mtrudel/bandit/commit/8156921a51e684a951221da7bc30a70a022f722e"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mtrudel/bandit"
    }
  ],
  "schema_version": "1.8.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "WebSocket permessage-deflate inflate has no output-size cap in bandit"
}