GHSA-79QM-7RJ5-M7R9
Vulnerability from github – Published: 2026-08-07 18:38 – Updated: 2026-08-07 18:38Summary
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.
{
"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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