CVE-2026-47675
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedHono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.21, the serialize() function in hono/cookie validates domain and path options against characters that corrupt Set-Cookie header syntax (;, \r, \n), but does not apply the same validation to sameSite and priority. An application that passes user-controlled input into either option may produce a Set-Cookie response header containing attacker-chosen additional attributes. This vulnerability is fixed in 4.12.21.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe serialize() function in Hono's cookie module validates domain and path options against malicious characters (;, \r, \n) that corrupt Set-Cookie header syntax, but lacks equivalent validation for sameSite and priority options. Attackers can pass crafted input to these unvalidated options to inject additional Set-Cookie header attributes, potentially hijacking cookies or causing other header injection effects.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 4.12.21CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check installed Hono versionRun `npm list hono` or inspect package.json to see the installed version of HonoAffected if The version is lower than 4.12.21 (e.g., 4.12.20, 4.11.0, etc.)
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Verify cookie serialize usageSearch codebase for imports of `serialize` from `@hono/cookie` or `hono/cookie` and usage of the serialize() functionAffected if The serialize() function is being called in your code
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Inspect sameSite option handlingReview serialize() calls and check if the `sameSite` option accepts values from user input (request parameters, headers, etc.) rather than hardcoded safe values (Strict, Lax, None)Affected if User-controlled input flows to the sameSite parameter without allowlist validation
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Inspect priority option handlingReview serialize() calls and check if the `priority` option accepts values from user input rather than hardcoded safe values (low, medium, high)Affected if User-controlled input flows to the priority parameter without allowlist validation
You are affected if using Hono version below 4.12.21 and passing user input directly to sameSite or priority options in the cookie serialize() function.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped4.12.21
Upgrade to Hono 4.12.21 or later. If unable to upgrade, implement explicit allowlist validation for sameSite (Strict/Lax/None) and priority (low/medium/high) options before passing user input to serialize().
4.12.21
- Upgrade the Hono package to version 4.12.21 or later by running: npm update hono or npm install [email protected]
- Verify the upgrade was successful by checking the installed version: npm list hono
- If using yarn: yarn upgrade [email protected]
- If using pnpm: pnpm update [email protected]
- Review application code that uses the cookie API to ensure user-controlled input is properly validated before passing to sameSite or priority options
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-47675 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-47675 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data