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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-71849: 0.36% estimated exploitation activity in the next 30 days; percentile 29.24 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

7 Aug 2026, 18:38 UTC

Last modified by the source

7 Aug 2026, 18:38 UTC

Source last checked

26 Oct 2026, 13:01 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-79qm-7rj5-m7r9

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# Patch Next advisory brief: CVE-2026-71849

Advisory: Hono: Proxy Helper does not remove response headers listed in the `Connection` header
IDs: CVE-2026-71849, GHSA-79qm-7rj5-m7r9
Record: https://patchnext.com/advisories/cve-2026-71849 (revision 1, source checked 26 Oct 2026, 13:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: hono 4.12.34. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm hono: affected >= 4.7.0, < 4.12.34; fixed in 4.12.34

## Suggested inspection (read-only)
- `npm ls hono --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on hono.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-79qm-7rj5-m7r9 (GitHub-reviewed advisory GHSA-79qm-7rj5-m7r9 lists affected ranges: npm hono >=4.7.0 <4.12.34)

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