GHSA-79QM-7RJ5-M7R9

Vulnerability from github – Published: 2026-08-07 18:38 – Updated: 2026-08-07 18:38
VLAI
Summary
Hono: Proxy Helper does not remove response headers listed in the `Connection` header
Details

Summary

The Proxy Helper (hono/proxy) does not remove response headers named by the origin's Connection header. Headers that the origin marked as connection-scoped are therefore forwarded to clients.

Details

Per RFC 9110 Section 7.6.1, an intermediary must remove the header fields listed in a message's Connection header field before forwarding the message, in addition to the well-known hop-by-hop headers. The proxy() function removed the well-known hop-by-hop headers (including Connection itself) from origin responses, but did not remove the headers that the response's Connection header field designated as connection-scoped.

This issue arises when an application proxies responses from an origin that declares additional, non-standard headers as hop-by-hop via the Connection response header.

Impact

A client may receive response headers that the origin intended only for its immediate peer. This may lead to:

  • Disclosure of connection-scoped or internal metadata contained in such headers

This issue affects applications that use the Proxy Helper (hono/proxy) to forward responses from origins that list custom header names in their Connection response header. Applications whose origins only use the standard hop-by-hop headers are not affected.

Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Show details on source website
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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "hono"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.7.0"
            },
            {
              "fixed": "4.12.34"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-71849"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-200"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-07T18:38:48Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "### Summary\n\nThe Proxy Helper (`hono/proxy`) does not remove response headers named by the origin\u0027s `Connection` header. Headers that the origin marked as connection-scoped are therefore forwarded to clients.\n\n### Details\n\nPer RFC 9110 Section 7.6.1, an intermediary must remove the header fields listed in a message\u0027s `Connection` header field before forwarding the message, in addition to the well-known hop-by-hop headers. The `proxy()` function removed the well-known hop-by-hop headers (including `Connection` itself) from origin responses, but did not remove the headers that the response\u0027s `Connection` header field designated as connection-scoped.\n\nThis issue arises when an application proxies responses from an origin that declares additional, non-standard headers as hop-by-hop via the `Connection` response header.\n\n### Impact\n\nA client may receive response headers that the origin intended only for its immediate peer. This may lead to:\n\n- Disclosure of connection-scoped or internal metadata contained in such headers\n\nThis issue affects applications that use the Proxy Helper (`hono/proxy`) to forward responses from origins that list custom header names in their `Connection` response header. Applications whose origins only use the standard hop-by-hop headers are not affected.",
  "id": "GHSA-79qm-7rj5-m7r9",
  "modified": "2026-08-07T18:38:48Z",
  "published": "2026-08-07T18:38:48Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/honojs/hono/security/advisories/GHSA-79qm-7rj5-m7r9"
    },
    {
      "type": "WEB",
      "url": "https://github.com/honojs/hono/commit/720b566290793d4358bf39843adcb7cf4da4548f"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/honojs/hono"
    },
    {
      "type": "WEB",
      "url": "https://github.com/honojs/hono/releases/tag/v4.12.34"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Hono: Proxy Helper does not remove response headers listed in the `Connection` header"
}



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