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Medium, CVSS 5.3amended

hono: AWS Lambda adapter merges multiple Set-Cookie headers into one value, dropping cookies on ALB single-header and Lattice

CVE-2026-54287GHSA-j6c9-x7qj-28xf

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (hono 4.12.25), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm hono

    Affected
    < 4.12.25
    Fixed in
    4.12.25

Sources

Severity and exploitation
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:L/A:N
EPSS
  • CVE-2026-54287: 0.31% estimated exploitation activity in the next 30 days; percentile 23.96 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary On AWS Lambda, the ALB single-header response and the VPC Lattice v2 response join multiple Set-Cookie headers into one comma-separated value. Because commas also appear inside cookie attributes (for example Expires dates), clients cannot split the value back into individual cookies and silently drop or misparse them. Details Per RFC 6265, each cookie must be its own Set-Cookie header line, and commas may appear inside attribute values. Joining cookies with ", " collides with those commas, producing a value that clients cannot reliably split. Only ALB single-header mode and VPC Lattice v2 are affected; API Gateway v1/v2 and ALB with multi-value headers enabled already use an array and are unaffected. Impact A client may receive only one of the cookies, a malformed cookie, or none. Session, CSRF, or preference cookies can silently fail to apply, breaking sessions or forcing re-authentication. This affects applications that set multiple cookies per response and run on AWS…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-j6c9-x7qj-28xf

  2. Revision 1 · created ·

    Published from osv record GHSA-j6c9-x7qj-28xf

Agent brief

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# Patch Next advisory brief: CVE-2026-54287

Advisory: hono: AWS Lambda adapter merges multiple `Set-Cookie` headers into one value, dropping cookies on ALB single-header and Lattice
IDs: CVE-2026-54287, GHSA-j6c9-x7qj-28xf
Record: https://patchnext.com/advisories/cve-2026-54287 (revision 2, source checked 26 Oct 2026, 12:57 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 4.12.25. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm hono: affected < 4.12.25; fixed in 4.12.25

## 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-j6c9-x7qj-28xf (OSV record GHSA-j6c9-x7qj-28xf lists affected ranges: npm hono >=0 <4.12.25 (fixed))
- Verified: https://github.com/advisories/GHSA-j6c9-x7qj-28xf (GitHub-reviewed advisory GHSA-j6c9-x7qj-28xf lists affected ranges: npm hono >=0 <4.12.25)

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