{"id":"CVE-2026-71849","aliases":["EUVD-2026-54579","GHSA-79qm-7rj5-m7r9"],"status":"published","title":"Hono: Proxy Helper does not remove response headers listed in the `Connection` header","description":"Hono is a Web application framework that provides support for any JavaScript runtime. From 4.7.0 to 4.12.33, the Proxy Helper proxy() function in hono/proxy does not remove response headers named by the origin's Connection header. 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, but the proxy() function only removed the well known hop by hop headers, including Connection itself, from origin responses. A client may therefore receive response headers that the origin intended only for its immediate peer, disclosing connection scoped or internal metadata contained in such headers, when an application proxies responses from an origin that declares additional, non standard headers as hop by hop via the Connection response header. This issue is fixed in version 4.12.34.","severity":{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00355,"percentile":0.29427,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-200"],"published":"2026-08-07T18:38:16Z","modified":"2026-10-28T02:30:59Z","fixes":[{"ecosystem":"npm","package":"hono","fixed_in":["4.12.34"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"hono","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.7.0"},{"fixed":"4.12.34"}]}]},{"source":"osv","ecosystem":"npm","package":"hono","ranges":[{"type":"SEMVER","events":[{"introduced":"4.7.0"},{"fixed":"4.12.34"}]}]}],"products":[{"vendor":"honojs","product":"hono"}],"references":[{"url":"https://github.com/honojs/hono/security/advisories/GHSA-79qm-7rj5-m7r9","tags":["x_refsource_CONFIRM","advisory","web"]},{"url":"https://github.com/honojs/hono/commit/720b566290793d4358bf39843adcb7cf4da4548f","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/honojs/hono/releases/tag/v4.12.34","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/advisories/GHSA-79qm-7rj5-m7r9"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/71xxx/CVE-2026-71849.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-71849","tags":["advisory"]},{"url":"https://github.com/honojs/hono","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-71849","title":"Hono: Proxy Helper does not remove response headers listed in the `Connection` header","description":"Hono is a Web application framework that provides support for any JavaScript runtime. From 4.7.0 to 4.12.33, the Proxy Helper proxy() function in hono/proxy does not remove response headers named by the origin's Connection header. 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, but the proxy() function only removed the well known hop by hop headers, including Connection itself, from origin responses. A client may therefore receive response headers that the origin intended only for its immediate peer, disclosing connection scoped or internal metadata contained in such headers, when an application proxies responses from an origin that declares additional, non standard headers as hop by hop via the Connection response header. This issue is fixed in version 4.12.34.","status":"published","published":"2026-08-07T18:38:16.287Z","modified":"2026-08-10T12:03:12.47Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low","assessor":"cna"}],"cwes":["CWE-200"],"updated_at":"2026-11-02T14:19:49.559463Z"}],"euvd":[{"id":"EUVD-2026-54579","description":"Hono is a Web application framework that provides support for any JavaScript runtime. From 4.7.0 to 4.12.33, the Proxy Helper proxy() function in hono/proxy does not remove response headers named by the origin's Connection header. 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, but the proxy() function only removed the well known hop by hop headers, including Connection itself, from origin responses. A client may therefore receive response headers that the origin intended only for its immediate peer, disclosing connection scoped or internal metadata contained in such headers, when an application proxies responses from an origin that declares additional, non standard headers as hop by hop via the Connection response header. This issue is fixed in version 4.12.34.","status":"published","published":"2026-08-07T18:38:16Z","modified":"2026-08-10T12:03:12Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"updated_at":"2026-11-02T18:02:05.732685Z"}],"ghsa":[{"id":"GHSA-79qm-7rj5-m7r9","title":"Hono: Proxy Helper does not remove response headers listed in the `Connection` header","description":"### 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.","status":"published","published":"2026-08-07T18:38:48Z","modified":"2026-08-07T18:38:49Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"cwes":["CWE-200"],"updated_at":"2026-11-02T14:40:58.888637Z"}],"nvd":[{"id":"CVE-2026-71849","description":"Hono is a Web application framework that provides support for any JavaScript runtime. From 4.7.0 to 4.12.33, the Proxy Helper proxy() function in hono/proxy does not remove response headers named by the origin's Connection header. 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, but the proxy() function only removed the well known hop by hop headers, including Connection itself, from origin responses. A client may therefore receive response headers that the origin intended only for its immediate peer, disclosing connection scoped or internal metadata contained in such headers, when an application proxies responses from an origin that declares additional, non standard headers as hop by hop via the Connection response header. This issue is fixed in version 4.12.34.","status":"published","published":"2026-08-07T19:18:54.1Z","modified":"2026-10-24T15:10:00.19Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low","assessor":"secondary"}],"cwes":["CWE-200"],"updated_at":"2026-11-02T14:12:35.743275Z"}],"osv":[{"id":"CVE-2026-71849","title":"Hono: Proxy Helper does not remove response headers listed in the `Connection` header","description":"Hono is a Web application framework that provides support for any JavaScript runtime. From 4.7.0 to 4.12.33, the Proxy Helper proxy() function in hono/proxy does not remove response headers named by the origin's Connection header. 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, but the proxy() function only removed the well known hop by hop headers, including Connection itself, from origin responses. A client may therefore receive response headers that the origin intended only for its immediate peer, disclosing connection scoped or internal metadata contained in such headers, when an application proxies responses from an origin that declares additional, non standard headers as hop by hop via the Connection response header. This issue is fixed in version 4.12.34.","status":"published","published":"2026-08-07T18:38:16.287Z","modified":"2026-10-28T02:30:59.873329482Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"cwes":["CWE-200"],"updated_at":"2026-11-02T15:45:15.511448Z"},{"id":"GHSA-79qm-7rj5-m7r9","title":"Hono: Proxy Helper does not remove response headers listed in the `Connection` header","description":"### 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.","status":"published","published":"2026-08-07T18:38:48Z","modified":"2026-09-10T03:51:13.317395159Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"cwes":["CWE-200"],"updated_at":"2026-11-02T15:46:41.002603Z"}]}}