Client-chosen HPACK encoder table size is applied uncapped, growing per-connection state with every response in Bandit

{
  "id": "b9d534211e472ab911eec2693f4e7566d61d0d944b5acfc02beae147adc1b9a2",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-110499",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Client-chosen HPACK encoder table size is applied uncapped, growing per-connection state with every response in Bandit",
    "summary": "Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to grow per-connection memory and CPU cost without bound via a large SETTINGS_HEADER_TABLE_SIZE. Bandit resizes its HPACK encoder table to whatever size the client advertises, up to 2^32-1 bytes, and indexes response headers into it. Because responses carry distinct values such as date or content-length, nothing is evicted and the table grows with every response for the life of the connection, while each lookup scans it linearly. The SETTINGS handling in Bandit.HTTP2.Connection (lib/bandit/http2/connection.ex) passes remote_settings.header_table_size to HPAX.resize/2 with no server-side cap, and encode_headers encodes every response header as :store. Serving N responses on one connection therefore costs O(N²) CPU in the connection process. This issue affects bandit: from 0.3.6 before 1.14.0.",
    "evidence": "cve:CVE-2026-110499",
    "products": [
      {
        "name": {
          "value": "bandit",
          "evidence": "/containers/cna/affected/0/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      },
      {
        "name": {
          "value": "bandit",
          "evidence": "/containers/cna/affected/1/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-110499",
      "aliases": [
        "CVE-2026-110499"
      ],
      "metrics": [
        {
          "format": "CVSS",
          "cvssV4_0": {
            "Safety": "NOT_DEFINED",
            "version": "4.0",
            "Recovery": "NOT_DEFINED",
            "baseScore": 8.7,
            "Automatable": "NOT_DEFINED",
            "attackVector": "NETWORK",
            "baseSeverity": "HIGH",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "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",
            "providerUrgency": "NOT_DEFINED",
            "userInteraction": "NONE",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "privilegesRequired": "NONE",
            "subIntegrityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "subAvailabilityImpact": "NONE",
            "vulnAvailabilityImpact": "HIGH",
            "subConfidentialityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
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              "lang": "en",
              "value": "GENERAL"
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      "affected": [
        {
          "cpes": [
            "cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"
          ],
          "repo": "https://github.com/mtrudel/bandit",
          "vendor": "mtrudel",
          "product": "bandit",
          "versions": [
            {
              "status": "affected",
              "version": "0.3.6",
              "lessThan": "1.14.0",
              "versionType": "semver"
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          ],
          "packageURL": "pkg:hex/bandit",
          "packageName": "bandit",
          "collectionURL": "https://repo.hex.pm",
          "defaultStatus": "unaffected"
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          "cpes": [
            "cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"
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          "repo": "https://github.com/mtrudel/bandit",
          "vendor": "mtrudel",
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          "packageURL": "pkg:github/mtrudel/bandit",
          "packageName": "mtrudel/bandit",
          "collectionURL": "https://github.com",
          "defaultStatus": "unaffected"
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      ],
      "modified": "2026-10-26T15:35:50.929Z",
      "provider": "cve",
      "references": [
        "https://github.com/mtrudel/bandit/security/advisories/GHSA-47x4-3fxf-82fr",
        "https://cna.erlef.org/cves/CVE-2026-110499.html",
        "https://osv.dev/vulnerability/EEF-CVE-2026-110499",
        "https://github.com/mtrudel/bandit/commit/0e68313fab9d204257ebad5c447e4cd9cea8e0ea",
        "https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a"
      ],
      "provider_metadata": {
        "adp": [
          {
            "title": "CISA ADP Vulnrichment",
            "metrics": [
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                "other": {
                  "type": "ssvc",
                  "content": {
                    "id": "CVE-2026-110499",
                    "role": "CISA Coordinator",
                    "options": [
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                        "Exploitation": "none"
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                        "Automatable": "yes"
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                        "Technical Impact": "partial"
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                    "version": "2.0.3",
                    "timestamp": "2026-10-26T15:02:00.207666Z"
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          "dateUpdated": "2026-10-26T13:32:38.613Z"
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    "related_cves": [
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        "value": "CVE-2026-110499",
        "evidence": "/cveMetadata/cveId"
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    "security_relevant": true,
    "severity_evidence": "/containers/cna/metrics"
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  "source_id": "core-cve",
  "document_id": 316040,
  "published_at": "2026-10-26T13:32:38.613+00:00"
}