{"id":"CVE-2026-71849","aliases":["GHSA-79qm-7rj5-m7r9"],"url":"https://o3.security/vulnerability/CVE-2026-71849","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.","published":"2026-08-07T18:38:16.287Z","modified":"2026-09-11T03:48:19.323197037Z","cvss":{"score":3.7,"severity":"LOW","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N"},"epss":{"score":0.00236,"percentile":0.14818,"asOf":"2026-08-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"hono","fixedVersion":"4.12.34"}],"fix":{"url":"https://github.com/honojs/hono/commit/720b566290793d4358bf39843adcb7cf4da4548f","label":"honojs/hono@720b566"},"references":[{"type":"WEB","url":"https://github.com/honojs/hono/releases/tag/v4.12.34"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/71xxx/CVE-2026-71849.json"},{"type":"ADVISORY","url":"https://github.com/honojs/hono/security/advisories/GHSA-79qm-7rj5-m7r9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-71849"},{"type":"FIX","url":"https://github.com/honojs/hono/commit/720b566290793d4358bf39843adcb7cf4da4548f"},{"type":"PACKAGE","url":"https://github.com/honojs/hono"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-11T03:48:19.323197037Z"}}