{"id":"GHSA-79qm-7rj5-m7r9","summary":"Hono: Proxy Helper does not remove response headers listed in the `Connection` header","details":"### Summary\n\nThe 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.\n\n### Details\n\nPer 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.\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.","aliases":["CVE-2026-71849"],"modified":"2026-08-07T18:56:13.005217Z","published":"2026-08-07T18:38:48Z","database_specific":{"cwe_ids":["CWE-200"],"severity":"LOW","github_reviewed":true,"github_reviewed_at":"2026-08-07T18:38:48Z","nvd_published_at":null},"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"}],"affected":[{"package":{"name":"hono","ecosystem":"npm","purl":"pkg:npm/hono"},"ranges":[{"type":"SEMVER","events":[{"introduced":"4.7.0"},{"fixed":"4.12.34"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/08/GHSA-79qm-7rj5-m7r9/GHSA-79qm-7rj5-m7r9.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N"}]}