Hono: Proxy Helper does not remove response headers listed in the `Connection` header

### 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.

Source published

7 Aug 2026 18:38:48 UTC

Source modified

10 Sep 2026 03:51:13 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Publisher rating · LOW