Hono missing validation of cookie name on write path in setCookie()

Exploitation

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

CVSS

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

EPSS

• CVE-2026-56762: 0.42% estimated exploitation activity in the next 30 days; percentile 36.17 (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 Cookie names are not validated on the write path when using setCookie(), serialize(), or serializeSigned() to generate Set-Cookie headers. While certain cookie attributes such as domain and path are validated, the cookie name itself may contain invalid characters. This results in inconsistent handling of cookie names between parsing (read path) and serialization (write path). Details When applications use setCookie(), serialize(), or serializeSigned() with a user-controlled cookie name, invalid values (e.g., containing control characters such as \r or \n) can be used to construct malformed Set-Cookie header values. For example: However, in modern runtimes such as Node.js and Cloudflare Workers, such invalid header values are rejected and result in a runtime error before the response is sent. As a result, the reported header injection / response splitting behavior could not be reproduced in these environments. Impact Applications that pass untrusted input as the cookie name to…

Published by the source

8 Apr 2026, 00:17 UTC

Last modified by the source

24 Sep 2026, 18:45 UTC

Source last checked

26 Oct 2026, 13:02 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-26pp-8wgv-hjvm

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-26pp-8wgv-hjvm

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# Patch Next advisory brief: CVE-2026-56762

Advisory: Hono missing validation of cookie name on write path in setCookie()
IDs: CVE-2026-56762, GHSA-26pp-8wgv-hjvm
Record: https://patchnext.com/advisories/cve-2026-56762 (revision 2, source checked 26 Oct 2026, 13:02 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: hono 4.12.12. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm hono: affected < 4.12.12; fixed in 4.12.12

## 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://osv.dev/vulnerability/GHSA-26pp-8wgv-hjvm (OSV record GHSA-26pp-8wgv-hjvm lists affected ranges: npm hono >=0 <4.12.12 (fixed))
- Verified: https://github.com/advisories/GHSA-26pp-8wgv-hjvm (GitHub-reviewed advisory GHSA-26pp-8wgv-hjvm lists affected ranges: npm hono >=0 <4.12.12)

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